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| author | Jann Horn <jannh@google.com> | 2025-03-27 00:04:36 +0300 |
|---|---|---|
| committer | Arnd Bergmann <arnd@arndb.de> | 2025-03-27 00:16:50 +0300 |
| commit | 47a60391ae0ed04ffbb9bd8dcd94ad9d08b41288 (patch) | |
| tree | 4ca8d7fa67a0c36b08931360d58569dfd0f53452 /include/asm-generic | |
| parent | ece69af2ede103e190ffdfccd9f9ec850606ab5e (diff) | |
| download | linux-47a60391ae0ed04ffbb9bd8dcd94ad9d08b41288.tar.xz | |
rwonce: fix crash by removing READ_ONCE() for unaligned read
When arm64 is built with LTO, it upgrades READ_ONCE() to ldar / ldapr
(load-acquire) to avoid issues that can be caused by the compiler
optimizing away implicit address dependencies.
Unlike plain loads, these load-acquire instructions actually require an
aligned address.
For now, fix it by removing the READ_ONCE() that the buggy commit
introduced.
Fixes: ece69af2ede1 ("rwonce: handle KCSAN like KASAN in read_word_at_a_time()")
Reported-by: Nathan Chancellor <nathan@kernel.org>
Closes: https://lore.kernel.org/r/20250326203926.GA10484@ax162
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Diffstat (limited to 'include/asm-generic')
| -rw-r--r-- | include/asm-generic/rwonce.h | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/include/asm-generic/rwonce.h b/include/asm-generic/rwonce.h index e9f2b84d2338..52b969c7cef9 100644 --- a/include/asm-generic/rwonce.h +++ b/include/asm-generic/rwonce.h @@ -86,7 +86,12 @@ unsigned long read_word_at_a_time(const void *addr) kasan_check_read(addr, 1); kcsan_check_read(addr, 1); - return READ_ONCE(*(unsigned long *)addr); + /* + * This load can race with concurrent stores to out-of-bounds memory, + * but READ_ONCE() can't be used because it requires higher alignment + * than plain loads in arm64 builds with LTO. + */ + return *(unsigned long *)addr; } #endif /* __ASSEMBLY__ */ |