linux-stable.git/arch/um/os-Linux, branch linux-6.13.y

um: remove copy_from_kernel_nofault_allowed

2025-04-10T12:41:49+00:00

[ Upstream commit 84a6fc378471fbeaf48f8604566a5a33a3d63c18 ]

There is no need to override the default version of this function
anymore as UML now has proper _nofault memory access functions.

Doing this also fixes the fact that the implementation was incorrect as
using mincore() will incorrectly flag pages as inaccessible if they were
swapped out by the host.

Fixes: f75b1b1bedfb ("um: Implement probe_kernel_read()")
Signed-off-by: Benjamin Berg 
Link: https://patch.msgid.link/20250210160926.420133-3-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg 
Signed-off-by: Sasha Levin

um: fix execve stub execution on old host OSs

2025-02-21T13:10:50+00:00

[ Upstream commit f82a9e7b9fa922bb9cccb00aae684a27b79e6df7 ]

The stub execution uses the somewhat new close_range and execveat
syscalls. Of these two, the execveat call is essential, but the
close_range call is more about stub process hygiene rather than safety
(and its result is ignored).

Replace both calls with a raw syscall as older machines might not have a
recent enough kernel for close_range (with CLOSE_RANGE_CLOEXEC) or a
libc that does not yet expose both of the syscalls.

Fixes: 32e8eaf263d9 ("um: use execveat to create userspace MMs")
Reported-by: Glenn Washburn 
Closes: https://lore.kernel.org/20250108022404.05e0de1e@crass-HP-ZBook-15-G2
Signed-off-by: Benjamin Berg 
Link: https://patch.msgid.link/20250113094107.674738-1-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg 
Signed-off-by: Richard Weinberger 
Signed-off-by: Sasha Levin

um: move thread info into task

2024-11-12T13:50:31+00:00

This selects the THREAD_INFO_IN_TASK option for UM and changes the way
that the current task is discovered. This is trivial though, as UML
already tracks the current task in cpu_tasks[] and this can be used to
retrieve it.

Also remove the signal handler code that copies the thread information
into the IRQ stack. It is obsolete now, which also means that the
mentioned race condition cannot happen anymore.

Signed-off-by: Benjamin Berg 
Reviewed-by: Hajime Tazaki 
Link: https://patch.msgid.link/20241111102910.46512-1-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg

um: remove broken double fault detection

2024-11-07T16:36:31+00:00

The show_stack function had some code to detect double faults. However,
the logic is wrong and it would e.g. trigger if a WARNING happened
inside an IRQ.

Remove it without trying to add a new logic. The current behaviour,
which will just fault repeatedly until the IRQ stack is used up and the
host kills UML, seems to be good enough.

Signed-off-by: Benjamin Berg 
Link: https://patch.msgid.link/20241103150506.1367695-5-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg

um: remove file sync for stub data

2024-11-07T16:36:30+00:00

There is no need to sync the stub code to "disk" for the other process
to see the correct memory. Drop the fsync there and remove the helper
function.

Signed-off-by: Benjamin Berg 
Link: https://patch.msgid.link/20241103150506.1367695-3-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg

um: always include kconfig.h and compiler-version.h

2024-11-07T16:36:30+00:00

Since commit a95b37e20db9 ("kbuild: get  out of
") we can safely include these files in userspace code.
Doing so simplifies matters as options do not need to be exported via
asm-offsets.h anymore.

Signed-off-by: Benjamin Berg 
Link: https://patch.msgid.link/20241103150506.1367695-2-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg

um: set DONTDUMP and DONTFORK flags on KASAN shadow memory

2024-11-07T16:36:30+00:00

There is no point in either dumping the KASAN shadow memory or doing
copy-on-write after a fork on these memory regions.

This considerably speeds up coredump generation.

Signed-off-by: Benjamin Berg 
Link: https://patch.msgid.link/20241103150506.1367695-1-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg

um: Set parent-death signal for write_sigio thread/process

2024-10-25T09:34:55+00:00

The write_sigio thread is not really a traditional thread. Set
the parent-death signal for it to ensure that it will be killed
if the UML kernel dies unexpectedly without proper cleanup.

Signed-off-by: Tiwei Bie 
Link: https://patch.msgid.link/20241024142828.2612828-4-tiwei.btw@antgroup.com
Signed-off-by: Johannes Berg

um: Add os_set_pdeathsig helper function

2024-10-25T09:34:54+00:00

This helper can be used to set the parent-death signal of the calling
process to SIGKILL to ensure that the process will be killed if the
UML kernel dies unexpectedly without proper cleanup. This helper will
be used in the follow-up patches.

Signed-off-by: Tiwei Bie 
Link: https://patch.msgid.link/20241024142828.2612828-2-tiwei.btw@antgroup.com
Signed-off-by: Johannes Berg

um: remove PATH_MAX use

2024-10-24T07:52:51+00:00

Evidently, PATH_MAX isn't always defined, at least not via .
Simply remove the use and replace it by a constant 4k. As stat::st_size
is zero for /proc/self/exe we can't even size it automatically, and it
seems unlikely someone's going to try to run UML with such a path.

Reported-by: kernel test robot 
Closes: https://lore.kernel.org/oe-kbuild-all/202410240553.gYNIXN8i-lkp@intel.com/
Fixes: 031acdcfb566 ("um: restore process name")
Signed-off-by: Johannes Berg