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authorEryu Guan <eguan@redhat.com>2017-10-13 15:58:18 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-10-13 16:18:33 -0700
commit7e86600606cef21beec725039d70377fb364f881 (patch)
tree786f8c72f935ad11d3f5213b335478f4a84e5e0c
parentf892760aa66a2d657deaf59538fb69433036767c (diff)
downloadlinux-sh-7e86600606cef21beec725039d70377fb364f881.tar.gz
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>
-rw-r--r--fs/binfmt_misc.c2
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);