linux-stable.git/samples, branch v6.18.51 Linux kernel stable tree samples/damon/wsse: stop and free damon ctx when damon_call() fails 2026-09-11T09:49:10+00:00 SJ Park sj@kernel.org 2026-06-28T21:54:44+00:00 cb55606449fd6d929be2d43face0f8e7b173acde commit a2c6fa6c23ad87c61e1379b05dc05cf5fed4bf8d upstream. damon_sample_wsse_start() calls damon_call() right after damon_start() is succeeded. The kdamond that has started by the damon_start() could be terminated by itself before or in the middle of the damon_call() execution. There could be multiple reasons for such a stop including monitoring target process termination and kdamond_fn() internal memory allocation failures. In the case, damon_call() will fail and return an error without cleaning up the DAMON context object. The damon_sample_wsse_start() caller assumes it would clean up the object, though. When the user requests to start DAMON again, damon_sample_wsse_start() is called again, allocates a new DAMON context object and overwrites the pointer for the previous object. As a result, the previous context object is leaked. Safely stop the kdamond and deallocate the context object when the failure is returned. Note that the kdamond should be stopped first, because damon_call() failure means not complete termination of the kdamond but only the fact that the termination process has started. The user impact shouldn't be that significant because the race is not easy to happen, and only up to one DAMON context object can be leaked per race. The issue was discovered [1] by Sashiko. Link: https://lore.kernel.org/20260628215447.96166-6-sj@kernel.org Link: https://lore.kernel.org/20260610034828.4632-1-sj@kernel.org [1] Fixes: cc9c1b8c205b ("samples/damon/wsse: use damon_call() repeat mode instead of damon_callback") Signed-off-by: SJ Park <sj@kernel.org> Reviewed-by: Zenghui Yu <zenghui.yu@linux.dev> Cc: <stable@vger.kernel.org> # 6.17.x Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit a2c6fa6c23ad87c61e1379b05dc05cf5fed4bf8d upstream.

damon_sample_wsse_start() calls damon_call() right after damon_start() is
succeeded.  The kdamond that has started by the damon_start() could be
terminated by itself before or in the middle of the damon_call()
execution.  There could be multiple reasons for such a stop including
monitoring target process termination and kdamond_fn() internal memory
allocation failures.  In the case, damon_call() will fail and return an
error without cleaning up the DAMON context object.  The
damon_sample_wsse_start() caller assumes it would clean up the object,
though.  When the user requests to start DAMON again,
damon_sample_wsse_start() is called again, allocates a new DAMON context
object and overwrites the pointer for the previous object.  As a result,
the previous context object is leaked.

Safely stop the kdamond and deallocate the context object when the failure
is returned.  Note that the kdamond should be stopped first, because
damon_call() failure means not complete termination of the kdamond but
only the fact that the termination process has started.

The user impact shouldn't be that significant because the race is not easy
to happen, and only up to one DAMON context object can be leaked per race.

The issue was discovered [1] by Sashiko.

Link: https://lore.kernel.org/20260628215447.96166-6-sj@kernel.org
Link: https://lore.kernel.org/20260610034828.4632-1-sj@kernel.org [1]
Fixes: cc9c1b8c205b ("samples/damon/wsse: use damon_call() repeat mode instead of damon_callback")
Signed-off-by: SJ Park <sj@kernel.org>
Reviewed-by: Zenghui Yu <zenghui.yu@linux.dev>
Cc: <stable@vger.kernel.org> # 6.17.x
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
samples/damon/wsse: handle damon_start() failure 2026-09-11T09:49:10+00:00 SJ Park sj@kernel.org 2026-06-28T21:54:40+00:00 6179c7f47876d576dfe30efa8fbf1b0b1fdd13c0 commit e4742be45ea45bf554399ce89a09f71e525d7981 upstream. Patch series "samples/damon: handle damon_{start,stop}() failures". All DAMON sample modules are not correctly handling failures from damon_start(). Among those, mtier also has an additional problem for handling of damon_stop() failures. wsse and prcl also have a problem in their damon_call() failure handling. As a result, memory leaks, next DAMON operation disruptions, and use-after-free can happen. Fix those. Note that only the damon_start() failure caused issues can reliably be reproduced. Reproducing those issues require the admin permission, though. This patch (of 6): damon_sample_wsse_start() callers assume it will clean up resources when it fails. And the function does the cleanup for context buildup failures. However, it is not doing the cleanup for damon_start() failure. As a result, when damon_start() fails, it leaks the memory for DAMON context. Free the context in case of the failure to fix the issues. Note that the issue can reliably be reproduced because the module calls damon_start() in the exclusive mode. For example, $ sudo damo start $ echo $$ | sudo tee /sys/module/damon_sample_wsse/parameters/target_pid $ echo Y | sudo tee /sys/module/damon_sample_wsse/parameters/enabled $ sudo cat /proc/allocinfo | grep damon_new_ctx Because the first command is running another DAMON instance, the third command fails the damon_start() call because the new DAMON instance cannot exclusively run. And without this fix, by repeating the third and the fourth commands above, we can show the memory consumption is only increasing due to the leaks. It requires the sudo permission though. The issue was discovered [1] by Sashiko. Link: https://lore.kernel.org/20260628215447.96166-2-sj@kernel.org Link: https://lore.kernel.org/20260609145814.70163-1-sj@kernel.org [1] Fixes: b757c6cfc696 ("samples/damon/wsse: start and stop DAMON as the user requests") Signed-off-by: SJ Park <sj@kernel.org> Reviewed-by: Zenghui Yu <zenghui.yu@linux.dev> Cc: <stable@vger.kernel.org> # 6.14.x Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit e4742be45ea45bf554399ce89a09f71e525d7981 upstream.

Patch series "samples/damon: handle damon_{start,stop}() failures".

All DAMON sample modules are not correctly handling failures from
damon_start().  Among those, mtier also has an additional problem for
handling of damon_stop() failures.  wsse and prcl also have a problem in
their damon_call() failure handling.  As a result, memory leaks, next
DAMON operation disruptions, and use-after-free can happen.  Fix those.

Note that only the damon_start() failure caused issues can reliably be
reproduced.  Reproducing those issues require the admin permission,
though.


This patch (of 6):

damon_sample_wsse_start() callers assume it will clean up resources when
it fails.  And the function does the cleanup for context buildup failures.
However, it is not doing the cleanup for damon_start() failure.  As a
result, when damon_start() fails, it leaks the memory for DAMON context.
Free the context in case of the failure to fix the issues.

Note that the issue can reliably be reproduced because the module calls
damon_start() in the exclusive mode.  For example,

    $ sudo damo start
    $ echo $$ | sudo tee /sys/module/damon_sample_wsse/parameters/target_pid
    $ echo Y | sudo tee /sys/module/damon_sample_wsse/parameters/enabled
    $ sudo cat /proc/allocinfo | grep damon_new_ctx

Because the first command is running another DAMON instance, the third
command fails the damon_start() call because the new DAMON instance cannot
exclusively run.  And without this fix, by repeating the third and the
fourth commands above, we can show the memory consumption is only
increasing due to the leaks.  It requires the sudo permission though.

The issue was discovered [1] by Sashiko.

Link: https://lore.kernel.org/20260628215447.96166-2-sj@kernel.org
Link: https://lore.kernel.org/20260609145814.70163-1-sj@kernel.org [1]
Fixes: b757c6cfc696 ("samples/damon/wsse: start and stop DAMON as the user requests")
Signed-off-by: SJ Park <sj@kernel.org>
Reviewed-by: Zenghui Yu <zenghui.yu@linux.dev>
Cc: <stable@vger.kernel.org> # 6.14.x
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
samples/damon/prcl: stop and free damon ctx when damon_call() fails 2026-09-11T09:49:10+00:00 SJ Park sj@kernel.org 2026-06-28T21:54:45+00:00 2446d3820cbaf88c386b8836194bdd42464115ec commit a73fa45d3f0f42c446ae55c5799e3d5ef044cd5d upstream. damon_sample_prcl_start() calls damon_call() right after damon_start() is succeeded. The kdamond that has started by the damon_start() could be terminated by itself before or in the middle of the damon_call() execution. There could be multiple reasons for such a stop including monitoring target process termination and kdamond_fn() internal memory allocation failures. In the case, damon_call() will fail and return an error without cleaning up the DAMON context object. The damon_sample_prcl_start() caller assumes it would clean up the object, though. When the user requests to start DAMON again, damon_sample_prcl_start() is called again, allocates a new DAMON context object and overwrites the pointer for the previous object. As a result, the previous context object is leaked. Safely stop the kdamond and deallocate the context object when the failure is returned. Note that the kdamond should be stopped first, because damon_call() failure means not complete termination of the kdamond but only the fact that the termination process has started. The user impact shouldn't be that significant because the race is not easy to happen, and only up to one DAMON context object can be leaked per race. The issue was discovered [1] by Sashiko. Link: https://lore.kernel.org/20260628215447.96166-7-sj@kernel.org Link: https://lore.kernel.org/20260610035214.4850-1-sj@kernel.org [1] Fixes: a6c33f1054e3 ("samples/damon/prcl: use damon_call() repeat mode instead of damon_callback") Signed-off-by: SJ Park <sj@kernel.org> Reviewed-by: Zenghui Yu <zenghui.yu@linux.dev> Cc: <stable@vger.kernel.org> # 6.17.x Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit a73fa45d3f0f42c446ae55c5799e3d5ef044cd5d upstream.

damon_sample_prcl_start() calls damon_call() right after damon_start() is
succeeded.  The kdamond that has started by the damon_start() could be
terminated by itself before or in the middle of the damon_call()
execution.  There could be multiple reasons for such a stop including
monitoring target process termination and kdamond_fn() internal memory
allocation failures.  In the case, damon_call() will fail and return an
error without cleaning up the DAMON context object.  The
damon_sample_prcl_start() caller assumes it would clean up the object,
though.  When the user requests to start DAMON again,
damon_sample_prcl_start() is called again, allocates a new DAMON context
object and overwrites the pointer for the previous object.  As a result,
the previous context object is leaked.

Safely stop the kdamond and deallocate the context object when the failure
is returned.  Note that the kdamond should be stopped first, because
damon_call() failure means not complete termination of the kdamond but
only the fact that the termination process has started.

The user impact shouldn't be that significant because the race is not easy
to happen, and only up to one DAMON context object can be leaked per race.

The issue was discovered [1] by Sashiko.

Link: https://lore.kernel.org/20260628215447.96166-7-sj@kernel.org
Link: https://lore.kernel.org/20260610035214.4850-1-sj@kernel.org [1]
Fixes: a6c33f1054e3 ("samples/damon/prcl: use damon_call() repeat mode instead of damon_callback")
Signed-off-by: SJ Park <sj@kernel.org>
Reviewed-by: Zenghui Yu <zenghui.yu@linux.dev>
Cc: <stable@vger.kernel.org> # 6.17.x
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
samples/damon/prcl: handle damon_start() failure 2026-09-11T09:49:10+00:00 SJ Park sj@kernel.org 2026-06-28T21:54:41+00:00 9f370353bba7f4bbe87a1c82fcf9f579ace1e3f1 commit 8b724349229bb6ebbf781178be011ba9bc2cca57 upstream. damon_sample_prcl_start() callers assume it will clean up resources when it fails. And the function does the cleanup for context buildup failures. However, it is not doing the cleanup for damon_start() failure. As a result, when damon_start() fails, it leaks the memory for DAMON context. Free the context in case of the failure to fix the issues. Note that the issue can reliably be reproduced because the module calls damon_start() in the exclusive mode. For example, $ sudo damo start $ echo $$ | sudo tee /sys/module/damon_sample_prcl/parameters/target_pid $ echo Y | sudo tee /sys/module/damon_sample_prcl/parameters/enabled $ sudo cat /proc/allocinfo | grep damon_new_ctx Because the first command is running another DAMON instance, the third command fails the damon_start() call because the new DAMON instance cannot exclusively run. And without this fix, by repeating the third and the fourth commands above, we can show the memory consumption is only increasing due to the leaks. It requires the sudo permission though. The issue was discovered [1] by Sashiko. Link: https://lore.kernel.org/20260628215447.96166-3-sj@kernel.org Link: https://lore.kernel.org/20260609145814.70163-1-sj@kernel.org [1] Fixes: 2aca254620a8 ("samples/damon: introduce a skeleton of a smaple DAMON module for proactive reclamation") Signed-off-by: SJ Park <sj@kernel.org> Reviewed-by: Zenghui Yu <zenghui.yu@linux.dev> Cc: <stable@vger.kernel.org> # 6.14.x Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 8b724349229bb6ebbf781178be011ba9bc2cca57 upstream.

damon_sample_prcl_start() callers assume it will clean up resources when
it fails.  And the function does the cleanup for context buildup failures.
However, it is not doing the cleanup for damon_start() failure.  As a
result, when damon_start() fails, it leaks the memory for DAMON context.
Free the context in case of the failure to fix the issues.

Note that the issue can reliably be reproduced because the module calls
damon_start() in the exclusive mode.  For example,

    $ sudo damo start
    $ echo $$ | sudo tee /sys/module/damon_sample_prcl/parameters/target_pid
    $ echo Y | sudo tee /sys/module/damon_sample_prcl/parameters/enabled
    $ sudo cat /proc/allocinfo | grep damon_new_ctx

Because the first command is running another DAMON instance, the third
command fails the damon_start() call because the new DAMON instance cannot
exclusively run.  And without this fix, by repeating the third and the
fourth commands above, we can show the memory consumption is only
increasing due to the leaks.  It requires the sudo permission though.

The issue was discovered [1] by Sashiko.

Link: https://lore.kernel.org/20260628215447.96166-3-sj@kernel.org
Link: https://lore.kernel.org/20260609145814.70163-1-sj@kernel.org [1]
Fixes: 2aca254620a8 ("samples/damon: introduce a skeleton of a smaple DAMON module for proactive reclamation")
Signed-off-by: SJ Park <sj@kernel.org>
Reviewed-by: Zenghui Yu <zenghui.yu@linux.dev>
Cc: <stable@vger.kernel.org> # 6.14.x
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
samples/damon/mtier: handle damon_stop() failure 2026-09-11T09:49:10+00:00 SJ Park sj@kernel.org 2026-06-28T21:54:43+00:00 3c07c57b894116ae26f01b84c68e68b538ada7ed commit 9dc5b6d66fd51b103eff21ed0df3e292f489ebc0 upstream. damon_sample_mtier_stop() assumes its damon_stop() call will always successfully stops the two DAMON contexts. Hence it deallocates the two DAMON contexts after the damon_stop() call. However, if a given context is already stopped, damon_stop() fails and returns an error while letting the DAMON contexts that have not yet stopped keep running. This kind of unexpected early DAMON context stops could happen due to memory allocation failures in kdamond_fn(). Because damon_sample_mtier_stop() just deallocates all DAMON contexts with damon_target and damon_region objects that are linked to the contexts, the execution of the unstopped DAMON context (kdamond) ends up using the memory that freed (use-after-free). Fix the issue by separating the damon_stop() to be invoked per context. Note that DAMON_SYSFS also allows multiple DAMON contexts execution. But, it calls damon_stop() for each context one by one. Hence this issue is only in mtier. For the long term, it would be better to refactor damon_stop() to always ensure stopping all contexts regardless of the failures in the middle. Make this fix in the current way, though, to keep it simple and easy to backport. I will do the refactoring later. The issue was discovered [1] by Sashiko. Link: https://lore.kernel.org/20260628215447.96166-5-sj@kernel.org Link: https://lore.kernel.org/20260609014219.3013-1-sj@kernel.org [1] Fixes: 82a08bde3cf7 ("samples/damon: implement a DAMON module for memory tiering") Signed-off-by: SJ Park <sj@kernel.org> Reviewed-by: Zenghui Yu <zenghui.yu@linux.dev> Cc: <stable@vger.kernel.org> # 6.16.x Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 9dc5b6d66fd51b103eff21ed0df3e292f489ebc0 upstream.

damon_sample_mtier_stop() assumes its damon_stop() call will always
successfully stops the two DAMON contexts.  Hence it deallocates the two
DAMON contexts after the damon_stop() call.  However, if a given context
is already stopped, damon_stop() fails and returns an error while letting
the DAMON contexts that have not yet stopped keep running.  This kind of
unexpected early DAMON context stops could happen due to memory allocation
failures in kdamond_fn().  Because damon_sample_mtier_stop() just
deallocates all DAMON contexts with damon_target and damon_region objects
that are linked to the contexts, the execution of the unstopped DAMON
context (kdamond) ends up using the memory that freed (use-after-free).
Fix the issue by separating the damon_stop() to be invoked per context.

Note that DAMON_SYSFS also allows multiple DAMON contexts execution.  But,
it calls damon_stop() for each context one by one.  Hence this issue is
only in mtier.

For the long term, it would be better to refactor damon_stop() to always
ensure stopping all contexts regardless of the failures in the middle.
Make this fix in the current way, though, to keep it simple and easy to
backport.  I will do the refactoring later.

The issue was discovered [1] by Sashiko.

Link: https://lore.kernel.org/20260628215447.96166-5-sj@kernel.org
Link: https://lore.kernel.org/20260609014219.3013-1-sj@kernel.org [1]
Fixes: 82a08bde3cf7 ("samples/damon: implement a DAMON module for memory tiering")
Signed-off-by: SJ Park <sj@kernel.org>
Reviewed-by: Zenghui Yu <zenghui.yu@linux.dev>
Cc: <stable@vger.kernel.org> # 6.16.x
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
samples/damon/mtier: handle damon_start() failure 2026-09-11T09:49:10+00:00 SJ Park sj@kernel.org 2026-06-28T21:54:42+00:00 f0808262a76165fbde6b4f1c2a8856a1e2b45512 commit c7230d08ee79b13127bd2b45a3648d361ac912fc upstream. damon_sample_mtier_start() callers assume it will clean up resources when it fails. And the function does the cleanup for context buildup failures. However, it is not doing the cleanup for damon_start() failure. As a result, when damon_start() fails, it could leak the memory for DAMON context. Also, if damon_start() fails for only the second context, the first context will indefinitely run, and avoid starting other DAMON contexts since it is running in the exclusive mode. Stop possibly started DAMON context and free the contexts in case of the failure to fix the issues. Note that the issue can reliably be reproduced because the module calls damon_start() in the exclusive mode. For example, $ sudo damo start $ echo Y | sudo tee /sys/module/damon_sample_mtier/parameters/enabled $ sudo cat /proc/allocinfo | grep damon_new_ctx Because the first command is running another DAMON instance, the second command fails the damon_start() call because the new DAMON instance cannot exclusively run. And without this fix, by repeating the second and the third commands above, we can show the memory consumption is only increasing due to the leaks. It requires the sudo permission though. The issue was discovered [1] by Sashiko. Link: https://lore.kernel.org/20260628215447.96166-4-sj@kernel.org Link: https://lore.kernel.org/20260608112455.274231F00893@smtp.kernel.org [1] Fixes: 82a08bde3cf7 ("samples/damon: implement a DAMON module for memory tiering") Signed-off-by: SJ Park <sj@kernel.org> Reviewed-by: Zenghui Yu <zenghui.yu@linux.dev> Cc: <stable@vger.kernel.org> # 6.16.x Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit c7230d08ee79b13127bd2b45a3648d361ac912fc upstream.

damon_sample_mtier_start() callers assume it will clean up resources when
it fails.  And the function does the cleanup for context buildup failures.
However, it is not doing the cleanup for damon_start() failure.

As a result, when damon_start() fails, it could leak the memory for DAMON
context.  Also, if damon_start() fails for only the second context, the
first context will indefinitely run, and avoid starting other DAMON
contexts since it is running in the exclusive mode.  Stop possibly started
DAMON context and free the contexts in case of the failure to fix the
issues.

Note that the issue can reliably be reproduced because the module calls
damon_start() in the exclusive mode.  For example,

    $ sudo damo start
    $ echo Y | sudo tee /sys/module/damon_sample_mtier/parameters/enabled
    $ sudo cat /proc/allocinfo | grep damon_new_ctx

Because the first command is running another DAMON instance, the second
command fails the damon_start() call because the new DAMON instance cannot
exclusively run.  And without this fix, by repeating the second and the
third commands above, we can show the memory consumption is only
increasing due to the leaks.  It requires the sudo permission though.

The issue was discovered [1] by Sashiko.

Link: https://lore.kernel.org/20260628215447.96166-4-sj@kernel.org
Link: https://lore.kernel.org/20260608112455.274231F00893@smtp.kernel.org [1]
Fixes: 82a08bde3cf7 ("samples/damon: implement a DAMON module for memory tiering")
Signed-off-by: SJ Park <sj@kernel.org>
Reviewed-by: Zenghui Yu <zenghui.yu@linux.dev>
Cc: <stable@vger.kernel.org> # 6.16.x
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
samples/damon/mtier: error out for zero quota goal target values 2026-08-19T16:18:16+00:00 SJ Park sj@kernel.org 2026-08-03T13:40:32+00:00 e16b8d640ec99b28bc827560edcf9706e610c3aa commit a16fd3ad9d89b05475864da97327870464611736 upstream. Patch series "mm/damon: avoid division by zero from damos_quota_score()". DAMON_SAMPLE_MTIER and DAMON_LRU_SORT allow the user to trigger division by zero in damos_quota_score(). Avoid it by adding parameters validation checks. This patch (of 2): damos_quota_score() can trigger division by zero if the target_value is zero. DAMON_SAMPLE_MTIER lets users set the target_value via node0_mem_{used,free}_bp parameters. It doesn't guard zero value case, though. As a result, users can trigger division by zero. Fix the issue by returning an error when the user tries to start DAMON with zero node0_mem_{used,free}_bp parameter values. DAMON_SAMPLE_MTIER is just a sample module, but the consequence is quite bad. Also the zero node0_mem_free_bp parameter might look like a reasonable setup to some users. Hence, the issue might really happen in the real world. One reliable way to reproduce the issue is like below: # cd /sys/module/damon_sample_mtier/parameters # echo 4096 > node0_start_addr # echo 8192 > node0_end_addr # echo 8192 > node1_start_addr # echo 81920 > node1_end_addr # echo 0 > node0_mem_free_bp # echo Y > enabled # dmesg -w [...] [18792.235916] Oops: divide error: 0000 [#1] SMP NOPTI [...] [18792.242787] RIP: 0010:damos_quota_score+0x6f/0x480 [...] This issue was discovered [1] by Sashiko. Link: https://lore.kernel.org/20260803134034.15217-1-sj@kernel.org Link: https://lore.kernel.org/20260803134034.15217-2-sj@kernel.org Link: https://lore.kernel.org/20260801202657.117135-1-sj@kernel.org [1] Fixes: c5e67d40a102 ("samples/damon/mtier: add parameters for node0 memory usage") Signed-off-by: SJ Park <sj@kernel.org> Cc: <stable@vger.kernel.org> # 6.17.x Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit a16fd3ad9d89b05475864da97327870464611736 upstream.

Patch series "mm/damon: avoid division by zero from damos_quota_score()".

DAMON_SAMPLE_MTIER and DAMON_LRU_SORT allow the user to trigger division
by zero in damos_quota_score().  Avoid it by adding parameters validation
checks.


This patch (of 2):

damos_quota_score() can trigger division by zero if the target_value is
zero.  DAMON_SAMPLE_MTIER lets users set the target_value via
node0_mem_{used,free}_bp parameters.  It doesn't guard zero value case,
though.  As a result, users can trigger division by zero.  Fix the issue
by returning an error when the user tries to start DAMON with zero
node0_mem_{used,free}_bp parameter values.

DAMON_SAMPLE_MTIER is just a sample module, but the consequence is quite
bad.  Also the zero node0_mem_free_bp parameter might look like a
reasonable setup to some users.  Hence, the issue might really happen in
the real world.

One reliable way to reproduce the issue is like below:

    # cd /sys/module/damon_sample_mtier/parameters
    # echo 4096 > node0_start_addr
    # echo 8192 > node0_end_addr
    # echo 8192 > node1_start_addr
    # echo 81920 > node1_end_addr
    # echo 0 > node0_mem_free_bp
    # echo Y > enabled
    # dmesg -w
    [...]
    [18792.235916] Oops: divide error: 0000 [#1] SMP NOPTI
    [...]
    [18792.242787] RIP: 0010:damos_quota_score+0x6f/0x480
    [...]

This issue was discovered [1] by Sashiko.

Link: https://lore.kernel.org/20260803134034.15217-1-sj@kernel.org
Link: https://lore.kernel.org/20260803134034.15217-2-sj@kernel.org
Link: https://lore.kernel.org/20260801202657.117135-1-sj@kernel.org [1]
Fixes: c5e67d40a102 ("samples/damon/mtier: add parameters for node0 memory usage")
Signed-off-by: SJ Park <sj@kernel.org>
Cc: <stable@vger.kernel.org> # 6.17.x
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
samples/damon/mtier: fail early if address range parameters are invalid 2026-07-24T14:17:25+00:00 Zenghui Yu yuzenghui@huawei.com 2026-06-29T14:44:31+00:00 9d360fb820a3b9576d155e720ec44fef54d2efb5 commit 7746d72c64054976887928d64d2caf25c5a6dcc0 upstream. The comment on top of `struct damon_region` clearly says that For any use case, @ar should be non-zero positive size. which is now verified in damon_verify_new_region() if the kernel is built with DAMON_DEBUG_SANITY. The WARN_ONCE() can be triggered if the mtier sample module is enabled before node{0,1}_{start,end}_addr have been properly initialized, which is obviously not good. ------------[ cut here ]------------ start 0 >= end 0 WARNING: mm/damon/core.c:217 at damon_new_region+0xf4/0x118, CPU#59: bash/341468 Call trace: damon_new_region+0xf4/0x118 (P) damon_set_regions+0xfc/0x3c0 damon_sample_mtier_build_ctx+0xe8/0x3a8 damon_sample_mtier_start+0x1c/0x90 damon_sample_mtier_enable_store+0x98/0xb0 param_attr_store+0xb4/0x128 module_attr_store+0x2c/0x50 sysfs_kf_write+0x58/0x90 kernfs_fop_write_iter+0x16c/0x238 vfs_write+0x2c0/0x370 ksys_write+0x74/0x118 __arm64_sys_write+0x24/0x38 invoke_syscall+0xa8/0x118 el0_svc_common.constprop.0+0x48/0xf0 do_el0_svc+0x24/0x38 el0_svc+0x54/0x370 el0t_64_sync_handler+0xa0/0xe8 el0t_64_sync+0x1ac/0x1b0 ---[ end trace 0000000000000000 ]--- Note that the same issue can happen if detect_node_addresses is true, and node 0 or 1 is memoryless. Fix it together by checking the validity of parameters right before damon_new_region() and fail early if they're invalid. Link: https://lore.kernel.org/20260629144432.133962-1-sj@kernel.org Fixes: 82a08bde3cf7 ("samples/damon: implement a DAMON module for memory tiering") Signed-off-by: Zenghui Yu <yuzenghui@huawei.com> Signed-off-by: SJ Park <sj@kernel.org> Reviewed-by: SJ Park <sj@kernel.org> Cc: <stable@vger.kernel.org> # 6.16.x Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 7746d72c64054976887928d64d2caf25c5a6dcc0 upstream.

The comment on top of `struct damon_region` clearly says that

    For any use case, @ar should be non-zero positive size.

which is now verified in damon_verify_new_region() if the kernel is built
with DAMON_DEBUG_SANITY.

The WARN_ONCE() can be triggered if the mtier sample module is enabled
before node{0,1}_{start,end}_addr have been properly initialized, which is
obviously not good.

 ------------[ cut here ]------------
 start 0 >= end 0
 WARNING: mm/damon/core.c:217 at damon_new_region+0xf4/0x118, CPU#59: bash/341468
 Call trace:
  damon_new_region+0xf4/0x118 (P)
  damon_set_regions+0xfc/0x3c0
  damon_sample_mtier_build_ctx+0xe8/0x3a8
  damon_sample_mtier_start+0x1c/0x90
  damon_sample_mtier_enable_store+0x98/0xb0
  param_attr_store+0xb4/0x128
  module_attr_store+0x2c/0x50
  sysfs_kf_write+0x58/0x90
  kernfs_fop_write_iter+0x16c/0x238
  vfs_write+0x2c0/0x370
  ksys_write+0x74/0x118
  __arm64_sys_write+0x24/0x38
  invoke_syscall+0xa8/0x118
  el0_svc_common.constprop.0+0x48/0xf0
  do_el0_svc+0x24/0x38
  el0_svc+0x54/0x370
  el0t_64_sync_handler+0xa0/0xe8
  el0t_64_sync+0x1ac/0x1b0
 ---[ end trace 0000000000000000 ]---

Note that the same issue can happen if detect_node_addresses is true, and
node 0 or 1 is memoryless.  Fix it together by checking the validity of
parameters right before damon_new_region() and fail early if they're
invalid.

Link: https://lore.kernel.org/20260629144432.133962-1-sj@kernel.org
Fixes: 82a08bde3cf7 ("samples/damon: implement a DAMON module for memory tiering")
Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
Signed-off-by: SJ Park <sj@kernel.org>
Reviewed-by: SJ Park <sj@kernel.org>
Cc: <stable@vger.kernel.org> # 6.16.x
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
tracing/events: Fix to check the simple_tsk_fn creation 2026-07-24T14:16:43+00:00 Masami Hiramatsu (Google) mhiramat@kernel.org 2026-06-24T23:34:46+00:00 e0881f5cc4d7130c5a70e96d37111f613ff06fc2 [ Upstream commit cda1fbfc5313bb90daa271d45eea4a8d317a8544 ] Sashiko pointed that this sample code does not correctly handle the failure of thread creation because kthread_run() can return -errno. Check the simple_tsk_fn is correctly initialized (created) or not. Link: https://lore.kernel.org/all/178165817322.269421.3992299509400184196.stgit@devnote2/ Link: https://sashiko.dev/#/patchset/178092865666.163648.10457567771536160909.stgit%40devnote2 Fixes: 9cfe06f8cd5c ("tracing/events: add trace-events-sample") Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit cda1fbfc5313bb90daa271d45eea4a8d317a8544 ]

Sashiko pointed that this sample code does not correctly handle the
failure of thread creation because kthread_run() can return -errno.

Check the simple_tsk_fn is correctly initialized (created) or not.

Link: https://lore.kernel.org/all/178165817322.269421.3992299509400184196.stgit@devnote2/

Link: https://sashiko.dev/#/patchset/178092865666.163648.10457567771536160909.stgit%40devnote2

Fixes: 9cfe06f8cd5c ("tracing/events: add trace-events-sample")
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
samples/ftrace: Adjust LoongArch register restore order in direct calls 2026-01-08T09:17:11+00:00 Chenghao Duan duanchenghao@kylinos.cn 2025-12-31T07:19:25+00:00 7d7010f5f0ee21dffeaad375949b2c7d431a2496 commit bb85d206be208bbf834883e948125a35ac59993a upstream. Ensure that in the ftrace direct call logic, the CPU register state (with ra = parent return address) is restored to the correct state after the execution of the custom trampoline function and before returning to the traced function. Additionally, guarantee the correctness of the jump logic for jr t0 (traced function address). Cc: stable@vger.kernel.org Fixes: 9cdc3b6a299c ("LoongArch: ftrace: Add direct call support") Reported-by: Youling Tang <tangyouling@kylinos.cn> Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org> Signed-off-by: Chenghao Duan <duanchenghao@kylinos.cn> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit bb85d206be208bbf834883e948125a35ac59993a upstream.

Ensure that in the ftrace direct call logic, the CPU register state
(with ra = parent return address) is restored to the correct state after
the execution of the custom trampoline function and before returning to
the traced function. Additionally, guarantee the correctness of the jump
logic for jr t0 (traced function address).

Cc: stable@vger.kernel.org
Fixes: 9cdc3b6a299c ("LoongArch: ftrace: Add direct call support")
Reported-by: Youling Tang <tangyouling@kylinos.cn>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Chenghao Duan <duanchenghao@kylinos.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>