diff options
| author | Eryu Guan <eguan@redhat.com> | 2017-10-13 15:58:18 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-10-13 16:18:33 -0700 |
| commit | 7e86600606cef21beec725039d70377fb364f881 (patch) | |
| tree | 786f8c72f935ad11d3f5213b335478f4a84e5e0c /fs/binfmt_misc.c | |
| parent | f892760aa66a2d657deaf59538fb69433036767c (diff) | |
| download | lwn-7e86600606cef21beec725039d70377fb364f881.tar.gz lwn-7e86600606cef21beec725039d70377fb364f881.zip | |
fs/binfmt_misc.c: node could be NULL when evicting inode
inode->i_private is assigned by a Node pointer only after registering a
new binary format, so it could be NULL if inode was created by
bm_fill_super() (or iput() was called by the error path in
bm_register_write()), and this could result in NULL pointer dereference
when evicting such an inode. e.g. mount binfmt_misc filesystem then
umount it immediately:
mount -t binfmt_misc binfmt_misc /proc/sys/fs/binfmt_misc
umount /proc/sys/fs/binfmt_misc
will result in
BUG: unable to handle kernel NULL pointer dereference at 0000000000000013
IP: bm_evict_inode+0x16/0x40 [binfmt_misc]
...
Call Trace:
evict+0xd3/0x1a0
iput+0x17d/0x1d0
dentry_unlink_inode+0xb9/0xf0
__dentry_kill+0xc7/0x170
shrink_dentry_list+0x122/0x280
shrink_dcache_parent+0x39/0x90
do_one_tree+0x12/0x40
shrink_dcache_for_umount+0x2d/0x90
generic_shutdown_super+0x1f/0x120
kill_litter_super+0x29/0x40
deactivate_locked_super+0x43/0x70
deactivate_super+0x45/0x60
cleanup_mnt+0x3f/0x70
__cleanup_mnt+0x12/0x20
task_work_run+0x86/0xa0
exit_to_usermode_loop+0x6d/0x99
syscall_return_slowpath+0xba/0xf0
entry_SYSCALL_64_fastpath+0xa3/0xa
Fix it by making sure Node (e) is not NULL.
Link: http://lkml.kernel.org/r/20171010100642.31786-1-eguan@redhat.com
Fixes: 83f918274e4b ("exec: binfmt_misc: shift filp_close(interp_file) from kill_node() to bm_evict_inode()")
Signed-off-by: Eryu Guan <eguan@redhat.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/binfmt_misc.c')
| -rw-r--r-- | fs/binfmt_misc.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c index 2a46762def31..a7c5a9861bef 100644 --- a/fs/binfmt_misc.c +++ b/fs/binfmt_misc.c @@ -596,7 +596,7 @@ static void bm_evict_inode(struct inode *inode) { Node *e = inode->i_private; - if (e->flags & MISC_FMT_OPEN_FILE) + if (e && e->flags & MISC_FMT_OPEN_FILE) filp_close(e->interp_file, NULL); clear_inode(inode); |