linux-stable.git/lib, branch v6.6.155

kcov: fix data corruption and race conditions on PREEMPT_RT

2026-08-27T12:29:45+00:00

commit 2eed77fdcb0cc48e8eccb2bcd4b7f2c6d650e84c upstream.

syzbot is reporting KCOV state corruption on PREEMPT_RT kernels, for the
temporary storage used for saving/restoring remote KCOV state is currently
allocated as the per-CPU area.

On PREEMPT_RT kernels, softirq handlers run as preemptible task threads
(e.g., ksoftirqd). If a softirq context preempts a task running a remote
KCOV session, it safely saves the task's state into the per-CPU area.
However, if that softirq thread is subsequently preempted by a higher-
priority softirq thread on the same CPU, the second softirq will overwrite
the same per-CPU area, permanently destroying the original task's KCOV
state.

Fix this data corruption by moving the temporary storage from the per-CPU
area to the per-thread area. Since each softirq thread now owns its own
task context, nested softirq preemption no longer causes data overwrites.

Note that while the temporary storage is now on a per-thread basis, the
per-CPU kcov_percpu_data.lock must be retained, for we need to ensure that
kcov_remote_start() and kcov_remote_stop() operate atomically without
racing against asynchronous interrupts that manipulate the current task's
KCOV state.

It is likely that GFP_KERNEL allocation by vmalloc_node() in kcov_init()
has already called panic() before returning NULL, for there will be no
OOM-killable userspace processes when __init function of built-in module
runs. But this patch also fixes crashing the kernel when vmalloc_node()
in kcov_init() returned NULL, for kcov_init() left per-CPU irq_area == NULL
but kcov_remote_start() depends on per-CPU irq_area != NULL, resulting in

  (1) doing vmalloc() in kcov_remote_start() despite !in_task() context

  (2) out-of-array-bounds access if (1) succeeded but
      kcov->remote_size < CONFIG_KCOV_IRQ_AREA_SIZE

  (3) always leak memory allocated by (1), eventually killing all
      OOM-killable userspace processes

problems.

Link: https://lore.kernel.org/43552d09-2ce2-4b19-b0d3-a2d1ab952145@I-love.SAKURA.ne.jp
Reported-by: syzbot+3f51ad7ac3ae57a6fdcc@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=3f51ad7ac3ae57a6fdcc
Reported-by: syzbot+47cf95ca1f9dcca872c8@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=47cf95ca1f9dcca872c8
Reported-by: syzbot+8a173e13208949931dc7@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=8a173e13208949931dc7
Reported-by: syzbot+90984d3713722683112e@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=90984d3713722683112e
Analyzed-by: AI Mode in Google Search (no mail address)
Fixes: 5ff3b30ab57d ("kcov: collect coverage from interrupts")
Signed-off-by: Tetsuo Handa 
Reviewed-by: Alexander Potapenko 
Cc: Alan Stern 
Cc: Andrey Konovalov 
Cc: Christoph Hellwig 
Cc: Clark Williams 
Cc: Dmitry Vyukov 
Cc: Greg Kroah-Hartman 
Cc: Marco Elver 
Cc: Mark Brown 
Cc: Roman Gushchin 
Cc: Sebastian Andrzej Siewior 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Greg Kroah-Hartman

fortify: Disable -Wstringop-overread in tests

2026-08-19T16:13:11+00:00

commit c1f3e770eec26d6f96dd6d2ea30555ba7c09a244 upstream.

clang recently added support for -Wstringop-overread [1], which is on by
default like -Wfortify-source. This breaks the usage of -Werror in the
fortify tests, resulting in the following false positive warnings in the
kernel build:

  warning: unsafe memcmp() usage lacked '__read_overflow2' warning in lib/test_fortify/read_overflow2-memcmp.c
  warning: unsafe memcmp() usage lacked '__read_overflow' warning in lib/test_fortify/read_overflow-memcmp.c
  warning: unsafe memchr() usage lacked '__read_overflow' warning in lib/test_fortify/read_overflow-memchr.c

Examining the fortify test logs shows a warning like the following in
each of the failed logs:

  In file included from lib/test_fortify/read_overflow2-memcmp.c:5:
  lib/test_fortify/test_fortify.h:34:2: error: 'memcmp' reading 17 bytes from a region of size 16 [-Werror,-Wstringop-overread]
     34 |         TEST;
        |         ^
  lib/test_fortify/read_overflow2-memcmp.c:3:2: note: expanded from macro 'TEST'
      3 |         memcmp(large, small, sizeof(small) + 1)
        |         ^
  1 error generated.

Disable -Wstringop-overread for the fortify tests, as it defeats the
purpose of testing the Linux specific implementation of fortify, like
-Wfortify-source.

Cc: stable@vger.kernel.org
Closes: https://github.com/ClangBuiltLinux/linux/issues/2168
Link: https://github.com/llvm/llvm-project/commit/86f2e71cb8d165b59ad31a442b2391e23826133e [1]
Signed-off-by: Nathan Chancellor 
Link: https://patch.msgid.link/20260623-fix-test_fortify-for-clang-stringop-overread-v1-1-15ee8342a953@kernel.org
Signed-off-by: Kees Cook 
Signed-off-by: Nathan Chancellor 
Signed-off-by: Sasha Levin

fortify: refactor test_fortify Makefile to fix some build problems

2026-08-19T16:13:11+00:00

commit 4e9903b0861c9df3464b82db4a7025863bac1897 upstream.

There are some issues in the test_fortify Makefile code.

Problem 1: cc-disable-warning invokes compiler dozens of times

To see how many times the cc-disable-warning is evaluated, change
this code:

  $(call cc-disable-warning,fortify-source)

to:

  $(call cc-disable-warning,$(shell touch /tmp/fortify-$$$$)fortify-source)

Then, build the kernel with CONFIG_FORTIFY_SOURCE=y. You will see a
large number of '/tmp/fortify-' files created:

  $ ls -1 /tmp/fortify-* | wc
       80      80    1600

This means the compiler was invoked 80 times just for checking the
-Wno-fortify-source flag support.

$(call cc-disable-warning,fortify-source) should be added to a simple
variable instead of a recursive variable.

Problem 2: do not recompile string.o when the test code is updated

The test cases are independent of the kernel. However, when the test
code is updated, $(obj)/string.o is rebuilt and vmlinux is relinked
due to this dependency:

  $(obj)/string.o: $(obj)/$(TEST_FORTIFY_LOG)

always-y is suitable for building the log files.

Problem 3: redundant code

  clean-files += $(addsuffix .o, $(TEST_FORTIFY_LOGS))

... is unneeded because the top Makefile globally cleans *.o files.

This commit fixes these issues and makes the code readable.

Signed-off-by: Masahiro Yamada 
Link: https://lore.kernel.org/r/20240727150302.1823750-2-masahiroy@kernel.org
Signed-off-by: Kees Cook 
[nathan: Fixed conflicts]
Signed-off-by: Nathan Chancellor 
Signed-off-by: Sasha Levin

rhashtable: clear stale iter->p on table restart

2026-08-09T18:21:50+00:00

[ Upstream commit 8173f7e2ce67e6ca1d4763f3da14e5b01ce77456 ]

rhashtable_walk_start_check() has two restart paths when resuming a walk.
When iter->walker.tbl is valid, it re-validates iter->p against the table
and sets iter->p = NULL if the object is gone.  When iter->walker.tbl is
NULL (table was freed during resize), it resets slot and skip but forgets
to clear iter->p.

rhashtable_walk_next() then dereferences the stale iter->p, reading
freed memory.  This is a use-after-free.

Any caller that does multi-fragment rhashtable walks across
walk_stop/walk_start boundaries is affected.  Concrete cases include
netlink_diag (__netlink_diag_dump in net/netlink/diag.c) and TIPC
(tipc_nl_sk_walk in net/tipc/socket.c).

Crash stack (netlink_diag):
  BUG: KASAN: slab-use-after-free in rhashtable_walk_next+0x365/0x3c0
  Read of size 8 at addr ffff88801a9d2438 (freed kmalloc-2k, offset 1080)
  Call Trace:
   rhashtable_walk_next+0x365/0x3c0 (lib/rhashtable.c:1016)
   __netlink_diag_dump+0x160/0x760 (net/netlink/diag.c:122)
   netlink_diag_dump+0xc2/0x240
   netlink_dump+0x5bc/0x1270
   netlink_recvmsg+0x7a3/0x980
   sock_recvmsg+0x1bc/0x200
   __sys_recvfrom+0x1d4/0x2c0

Fixes: 5d240a8936f6 ("rhashtable: improve rhashtable_walk stability when stop/start used.")
Cc: 
Reported-by: AutonomousCodeSecurity@microsoft.com
Reported-by: Yuan Tan 
Closes: https://lore.kernel.org/linux-crypto/CAB8m9Wh559e+=n8z51gB8DrbEyCc2mc0MgGjrRR6_VXBmU=2AQ@mail.gmail.com
Signed-off-by: Cen Zhang (Microsoft) 
Reviewed-by: NeilBrown 
Signed-off-by: Herbert Xu 
Signed-off-by: Sasha Levin

assoc_array: trim the final shortcut word using the current chunk end

2026-08-09T18:21:46+00:00

[ Upstream commit a82c8a05e86f3f84e09698f65b4515b5d04633f6 ]

assoc_array_walk() masks off the bits past shortcut->skip_to_level in the
word that contains skip_to_level, gated on
round_up(sc_level, ASSOC_ARRAY_KEY_CHUNK_SIZE) > skip_to_level.

That guard is wrong in two opposite ways:

 - When sc_level is word-aligned (every word after the first) round_up()
   is a no-op, so the guard is sc_level > skip_to_level and never fires for
   the word that holds skip_to_level.  A shortcut that spans more than one
   word and ends in the middle of its last word leaves that word untrimmed,
   and its stale high bits leak into the dissimilarity word and can steer
   the walk down the wrong descendant.

 - When sc_level is unaligned (the first word) and skip_to_level sits on
   the next chunk boundary, sc_level + CHUNK would exceed skip_to_level and
   fire the trim with shift = skip_to_level & CHUNK_MASK == 0, which clears
   the whole dissimilarity word and makes a differing shortcut compare
   equal.

Use the end of the chunk that contains sc_level instead:

	skip_to_level < round_down(sc_level, CHUNK) + CHUNK

For an aligned sc_level whose word holds skip_to_level this now fires (the
first bug); for an unaligned sc_level with skip_to_level on the following
boundary it does not, so shift is never 0 when the branch runs and the trim
never clears the whole word.

Fixes: 3cb989501c26 ("Add a generic associative array implementation.")
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Michael Bommarito 
Reviewed-by: Jarkko Sakkinen 
Tested-by: Jarkko Sakkinen 
Link: https://lore.kernel.org/r/20260719161505.2423935-4-michael.bommarito@gmail.com
Signed-off-by: Jarkko Sakkinen 
Signed-off-by: Sasha Levin

bootconfig: fix NULL-pointer arithmetic in xbc_snprint_cmdline()

2026-08-03T09:15:39+00:00

[ Upstream commit dec4d8118c179b3d12bca7e609054c6011c4f2ce ]

xbc_snprint_cmdline() is meant to be called twice: first with
buf=NULL, size=0 to probe the rendered length, then with a real
buffer to fill it (the standard snprintf() two-pass pattern). The
probe call makes the function compute "buf + size" (NULL + 0) and,
on every iteration, advance "buf += ret" from that NULL base and
pass the result back into snprintf().

Pointer arithmetic on a NULL pointer is undefined behavior. It is
harmless in the in-kernel callers today, but the follow-up patches
run this same code in the userspace tools/bootconfig parser at kernel
build time, where host UBSan / FORTIFY_SOURCE abort the build.

Track a running written length (size_t) instead of mutating @buf, and
only form "buf + len" when @buf is non-NULL. snprintf(NULL, 0, ...)
is itself well defined and returns the would-be length, so the
two-pass "probe then fill" usage returns identical byte counts.

Link: https://lore.kernel.org/all/20260626-bootconfig_using_tools-v7-1-24ab72139c29@debian.org/

Fixes: 51887d03aca1 ("bootconfig: init: Allow admin to use bootconfig for kernel command line")
Cc: stable@vger.kernel.org
Signed-off-by: Breno Leitao 
Signed-off-by: Masami Hiramatsu (Google) 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

bootconfig: move xbc_snprint_cmdline() to lib/bootconfig.c

2026-08-03T09:15:39+00:00

[ Upstream commit 5a643e4623238e14b03d75ca0d4eda0645720cee ]

Move xbc_snprint_cmdline() from init/main.c to lib/bootconfig.c so the
function (and its xbc_namebuf scratch buffer) becomes part of the shared
parser library. tools/bootconfig already compiles lib/bootconfig.c
directly, which lets a follow-up patch reuse the same renderer in the
userspace tool to convert a bootconfig file into a flat cmdline string
at build time.

No functional change.

Link: https://lore.kernel.org/all/20260508-bootconfig_using_tools-v1-1-1132219aa773@debian.org/

Signed-off-by: Breno Leitao 
Signed-off-by: Masami Hiramatsu (Google) 
Stable-dep-of: dec4d8118c17 ("bootconfig: fix NULL-pointer arithmetic in xbc_snprint_cmdline()")
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

audit: use 'unsigned int' instead of 'unsigned'

2026-08-03T09:15:34+00:00

[ Upstream commit 8b226771014beab1292081151a99530886ce54b4 ]

Address checkpatch.pl warning below, across the audit subsystem:

  WARNING: Prefer 'unsigned int' to bare use of 'unsigned'

Minor cleanup, no functional changes.

Signed-off-by: Ricardo Robaina 
Signed-off-by: Paul Moore 
Stable-dep-of: 81905b5acbe7 ("audit: fix recursive locking deadlock in audit_dupe_exe()")
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

lib/test_meminit: use && for bools

2026-07-24T14:03:06+00:00

[ Upstream commit 8e0c2085c978ed6d9764d79fc785920360096f21 ]

As pointed out by Dan Carpenter, test_kmemcache() was using a bitwise AND
on two bools instead of a boolean AND.  Fix this for the sake of code
cleanliness.

Link: https://lore.kernel.org/20260504100637.1535762-1-glider@google.com
Fixes: 5015a300a522 ("lib: introduce test_meminit module")
Signed-off-by: Alexander Potapenko 
Reported-by: Dan Carpenter 
Closes: https://lore.kernel.org/kernel-janitors/afOcIan1ap9kD26M@stanley.mountain/
Reviewed-by: Andrew Morton 
Signed-off-by: Andrew Morton 
Signed-off-by: Sasha Levin

tracing: Prevent out-of-bounds read in glob matching

2026-07-24T14:02:54+00:00

commit 0a6070839b1ef276d5b05bedfb787743e140fb17 upstream.

String event fields are not necessarily NUL-terminated, so the filter
predicate functions (filter_pred_string(), filter_pred_strloc() and
filter_pred_strrelloc()) pass the field length to the regex match
callbacks, and the length-aware matchers honour it.

regex_match_glob() was the exception: it ignored the length and called
glob_match(), which scans the string until it hits a NUL byte. Some
string fields are not NUL-terminated. One example is the dynamic char
array of the xfs_* namespace tracepoints, which is copied without a
trailing NUL. For such a field, glob matching reads past the end of
the event field, causing a KASAN slab-out-of-bounds read in
glob_match(), reached via regex_match_glob() and filter_match_preds()
from the xfs_lookup tracepoint.

Add a length-bounded glob_match_len() and use it from regex_match_glob()
so glob matching always stops at the field boundary. The matching loop
is factored into a shared helper so glob_match() keeps its behaviour.

Fixes: 60f1d5e3bac4 ("ftrace: Support full glob matching")
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/da1aaf125fc3b63320b0c540fd6afa7c3d5b4f1a.1782836943.git.hhhuang@smu.edu.sg
Reported-by: Yuan Tan 
Reported-by: Yifan Wu 
Reported-by: Juefei Pu 
Reported-by: Zhengchuan Liang 
Reported-by: Xin Liu 
Assisted-by: Codex:GPT-5.4
Signed-off-by: Huihui Huang 
Signed-off-by: Ren Wei 
Acked-by: Masami Hiramatsu (Google) 
Signed-off-by: Steven Rostedt 
Signed-off-by: Greg Kroah-Hartman