MIRRORS/linux-yocto
1
0
Fork 0
mirror of git://git.yoctoproject.org/linux-yocto.git synced 2025-10-22 15:03:53 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity
a9152eb181
linux-yocto/mm/kmsan
History
Eric Biggers f84e487070 kmsan: fix out-of-bounds access to shadow memory 
commit 85e1ff61060a765d91ee62dc5606d4d547d9d105 upstream.

Running sha224_kunit on a KMSAN-enabled kernel results in a crash in
kmsan_internal_set_shadow_origin():

    BUG: unable to handle page fault for address: ffffbc3840291000
    #PF: supervisor read access in kernel mode
    #PF: error_code(0x0000) - not-present page
    PGD 1810067 P4D 1810067 PUD 192d067 PMD 3c17067 PTE 0
    Oops: 0000 [#1] SMP NOPTI
    CPU: 0 UID: 0 PID: 81 Comm: kunit_try_catch Tainted: G                 N  6.17.0-rc3 #10 PREEMPT(voluntary)
    Tainted: [N]=TEST
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.17.0-0-gb52ca86e094d-prebuilt.qemu.org 04/01/2014
    RIP: 0010:kmsan_internal_set_shadow_origin+0x91/0x100
    [...]
    Call Trace:
    <TASK>
    __msan_memset+0xee/0x1a0
    sha224_final+0x9e/0x350
    test_hash_buffer_overruns+0x46f/0x5f0
    ? kmsan_get_shadow_origin_ptr+0x46/0xa0
    ? __pfx_test_hash_buffer_overruns+0x10/0x10
    kunit_try_run_case+0x198/0xa00

This occurs when memset() is called on a buffer that is not 4-byte aligned
and extends to the end of a guard page, i.e.  the next page is unmapped.

The bug is that the loop at the end of kmsan_internal_set_shadow_origin()
accesses the wrong shadow memory bytes when the address is not 4-byte
aligned.  Since each 4 bytes are associated with an origin, it rounds the
address and size so that it can access all the origins that contain the
buffer.  However, when it checks the corresponding shadow bytes for a
particular origin, it incorrectly uses the original unrounded shadow
address.  This results in reads from shadow memory beyond the end of the
buffer's shadow memory, which crashes when that memory is not mapped.

To fix this, correctly align the shadow address before accessing the 4
shadow bytes corresponding to each origin.

Link: https://lkml.kernel.org/r/20250911195858.394235-1-ebiggers@kernel.org
Fixes: 2ef3cec44c ("kmsan: do not wipe out origin when doing partial unpoisoning")
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Tested-by: Alexander Potapenko <glider@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2025-10-02 13:44:14 +02:00
..
core.c kmsan: fix out-of-bounds access to shadow memory 2025-10-02 13:44:14 +02:00
hooks.c dma: kmsan: export kmsan_handle_dma() for modules 2025-03-13 13:01:58 +01:00
init.c kmsan: accept ranges starting with 0 on s390 2024-07-03 19:30:23 -07:00
instrumentation.c kmsan: do not pass NULL pointers as 0 2024-07-03 19:30:26 -07:00
kmsan_test.c kmsan: fix out-of-bounds access to shadow memory 2025-10-02 13:44:14 +02:00
kmsan.h kmsan: add missing __user tags 2024-07-03 19:30:26 -07:00
Makefile
report.c kmsan: add missing __user tags 2024-07-03 19:30:26 -07:00
shadow.c