[ Upstream commit e3f269ed0accbb22aa8f25d2daffa23c3fccd407 ]
Since:
7ee18d677989 ("x86/power: Make restore_processor_context() sane")
kmemleak reports this issue:
unreferenced object 0xf68241e0 (size 32):
comm "swapper/0", pid 1, jiffies 4294668610 (age 68.432s)
hex dump (first 32 bytes):
00 cc cc cc 29 10 01 c0 00 00 00 00 00 00 00 00 ....)...........
00 42 82 f6 cc cc cc cc cc cc cc cc cc cc cc cc .B..............
backtrace:
[<461c1d50>] __kmem_cache_alloc_node+0x106/0x260
[<ea65e13b>] __kmalloc+0x54/0x160
[<c3858cd2>] msr_build_context.constprop.0+0x35/0x100
[<46635aff>] pm_check_save_msr+0x63/0x80
[<6b6bb938>] do_one_initcall+0x41/0x1f0
[<3f3add60>] kernel_init_freeable+0x199/0x1e8
[<3b538fde>] kernel_init+0x1a/0x110
[<938ae2b2>] ret_from_fork+0x1c/0x28
Which is a false positive.
Reproducer:
- Run rsync of whole kernel tree (multiple times if needed).
- start a kmemleak scan
- Note this is just an example: a lot of our internal tests hit these.
The root cause is similar to the fix in:
b0b592cf0836 x86/pm: Fix false positive kmemleak report in msr_build_context()
ie. the alignment within the packed struct saved_context
which has everything unaligned as there is only "u16 gs;" at start of
struct where in the past there were four u16 there thus aligning
everything afterwards. The issue is with the fact that Kmemleak only
searches for pointers that are aligned (see how pointers are scanned in
kmemleak.c) so when the struct members are not aligned it doesn't see
them.
Testing:
We run a lot of tests with our CI, and after applying this fix we do not
see any kmemleak issues any more whilst without it we see hundreds of
the above report. From a single, simple test run consisting of 416 individual test
cases on kernel 5.10 x86 with kmemleak enabled we got 20 failures due to this,
which is quite a lot. With this fix applied we get zero kmemleak related failures.
Fixes: 7ee18d677989 ("x86/power: Make restore_processor_context() sane")
Signed-off-by: Anton Altaparmakov <anton@tuxera.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: stable@vger.kernel.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20240314142656.17699-1-anton@tuxera.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 3fb0fdb3bbe7aed495109b3296b06c2409734023 ]
On 32-bit kernels, the stackprotector canary is quite nasty -- it is
stored at %gs:(20), which is nasty because 32-bit kernels use %fs for
percpu storage. It's even nastier because it means that whether %gs
contains userspace state or kernel state while running kernel code
depends on whether stackprotector is enabled (this is
CONFIG_X86_32_LAZY_GS), and this setting radically changes the way
that segment selectors work. Supporting both variants is a
maintenance and testing mess.
Merely rearranging so that percpu and the stack canary
share the same segment would be messy as the 32-bit percpu address
layout isn't currently compatible with putting a variable at a fixed
offset.
Fortunately, GCC 8.1 added options that allow the stack canary to be
accessed as %fs:__stack_chk_guard, effectively turning it into an ordinary
percpu variable. This lets us get rid of all of the code to manage the
stack canary GDT descriptor and the CONFIG_X86_32_LAZY_GS mess.
(That name is special. We could use any symbol we want for the
%fs-relative mode, but for CONFIG_SMP=n, gcc refuses to let us use any
name other than __stack_chk_guard.)
Forcibly disable stackprotector on older compilers that don't support
the new options and turn the stack canary into a percpu variable. The
"lazy GS" approach is now used for all 32-bit configurations.
Also makes load_gs_index() work on 32-bit kernels. On 64-bit kernels,
it loads the GS selector and updates the user GSBASE accordingly. (This
is unchanged.) On 32-bit kernels, it loads the GS selector and updates
GSBASE, which is now always the user base. This means that the overall
effect is the same on 32-bit and 64-bit, which avoids some ifdeffery.
[ bp: Massage commit message. ]
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/c0ff7dba14041c7e5d1cae5d4df052f03759bef3.1613243844.git.luto@kernel.org
Stable-dep-of: e3f269ed0acc ("x86/pm: Work around false positive kmemleak report in msr_build_context()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
