diff options
| author | Tu Jinjiang <tujinjiang@huawei.com> | 2023-05-25 11:16:40 +0800 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2023-06-09 16:25:43 -0700 |
| commit | 283ebdee2da30f65cba04c8fe690b97acfc7f4c4 (patch) | |
| tree | 2ca3850217d4ae1b60d6a585f2392f5e63174e91 /mm/shmem.c | |
| parent | a8d13355c660255266ece529e81e6cb26754941a (diff) | |
| download | linux-283ebdee2da30f65cba04c8fe690b97acfc7f4c4.tar.gz | |
mm: shmem: fix UAF bug in shmem_show_options()
shmem_show_options() uses sbinfo->mpol without adding it's refcnt. This
may lead to race with replacement of the mpol by remount. The execution
sequence is as follows.
CPU0 CPU1
shmem_show_options() shmem_reconfigure()
shmem_show_mpol(seq, sbinfo->mpol) mpol = sbinfo->mpol
mpol_put(mpol)
mpol->mode
The KASAN report is as follows.
BUG: KASAN: slab-use-after-free in shmem_show_options+0x21b/0x340
Read of size 2 at addr ffff888124324004 by task mount/2388
CPU: 2 PID: 2388 Comm: mount Not tainted 6.4.0-rc3-00017-g9d646009f65d-dirty #8
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x37/0x50
print_report+0xd0/0x620
? shmem_show_options+0x21b/0x340
? __virt_addr_valid+0xf4/0x180
? shmem_show_options+0x21b/0x340
kasan_report+0xb8/0xe0
? shmem_show_options+0x21b/0x340
shmem_show_options+0x21b/0x340
? __pfx_shmem_show_options+0x10/0x10
? strchr+0x2c/0x50
? strlen+0x23/0x40
? seq_puts+0x7d/0x90
show_vfsmnt+0x1e6/0x260
? __pfx_show_vfsmnt+0x10/0x10
? __kasan_kmalloc+0x7f/0x90
seq_read_iter+0x57a/0x740
vfs_read+0x2e2/0x4a0
? __pfx_vfs_read+0x10/0x10
? down_write_killable+0xb8/0x140
? __pfx_down_write_killable+0x10/0x10
? __fget_light+0xa9/0x1e0
? up_write+0x3f/0x80
ksys_read+0xb8/0x150
? __pfx_ksys_read+0x10/0x10
? fpregs_assert_state_consistent+0x55/0x60
? exit_to_user_mode_prepare+0x2d/0x120
do_syscall_64+0x3c/0x90
entry_SYSCALL_64_after_hwframe+0x72/0xdc
</TASK>
Allocated by task 2387:
kasan_save_stack+0x22/0x50
kasan_set_track+0x25/0x30
__kasan_slab_alloc+0x59/0x70
kmem_cache_alloc+0xdd/0x220
mpol_new+0x83/0x150
mpol_parse_str+0x280/0x4a0
shmem_parse_one+0x364/0x520
vfs_parse_fs_param+0xf8/0x1a0
vfs_parse_fs_string+0xc9/0x130
shmem_parse_options+0xb2/0x110
path_mount+0x597/0xdf0
do_mount+0xcd/0xf0
__x64_sys_mount+0xbd/0x100
do_syscall_64+0x3c/0x90
entry_SYSCALL_64_after_hwframe+0x72/0xdc
Freed by task 2389:
kasan_save_stack+0x22/0x50
kasan_set_track+0x25/0x30
kasan_save_free_info+0x2e/0x50
__kasan_slab_free+0x10e/0x1a0
kmem_cache_free+0x9c/0x350
shmem_reconfigure+0x278/0x370
reconfigure_super+0x383/0x450
path_mount+0xcc5/0xdf0
do_mount+0xcd/0xf0
__x64_sys_mount+0xbd/0x100
do_syscall_64+0x3c/0x90
entry_SYSCALL_64_after_hwframe+0x72/0xdc
The buggy address belongs to the object at ffff888124324000
which belongs to the cache numa_policy of size 32
The buggy address is located 4 bytes inside of
freed 32-byte region [ffff888124324000, ffff888124324020)
==================================================================
To fix the bug, shmem_get_sbmpol() / mpol_put() needs to be called
before / after shmem_show_mpol() call.
Link: https://lkml.kernel.org/r/20230525031640.593733-1-tujinjiang@huawei.com
Signed-off-by: Tu Jinjiang <tujinjiang@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Nanyong Sun <sunnanyong@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/shmem.c')
| -rw-r--r-- | mm/shmem.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/mm/shmem.c b/mm/shmem.c index e40a08c5c6d78a..5e54ab5f61f2e6 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -3726,6 +3726,7 @@ out: static int shmem_show_options(struct seq_file *seq, struct dentry *root) { struct shmem_sb_info *sbinfo = SHMEM_SB(root->d_sb); + struct mempolicy *mpol; if (sbinfo->max_blocks != shmem_default_max_blocks()) seq_printf(seq, ",size=%luk", @@ -3768,7 +3769,9 @@ static int shmem_show_options(struct seq_file *seq, struct dentry *root) if (sbinfo->huge) seq_printf(seq, ",huge=%s", shmem_format_huge(sbinfo->huge)); #endif - shmem_show_mpol(seq, sbinfo->mpol); + mpol = shmem_get_sbmpol(sbinfo); + shmem_show_mpol(seq, mpol); + mpol_put(mpol); if (sbinfo->noswap) seq_printf(seq, ",noswap"); return 0; |