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David Howells 278eb88ab2 afs: Fix NULL deref in afs_dynroot_depopulate() 
[ Upstream commit 5e0b17b026 ]

If an error occurs during the construction of an afs superblock, it's
possible that an error occurs after a superblock is created, but before
we've created the root dentry.  If the superblock has a dynamic root
(ie.  what's normally mounted on /afs), the afs_kill_super() will call
afs_dynroot_depopulate() to unpin any created dentries - but this will
oops if the root hasn't been created yet.

Fix this by skipping that bit of code if there is no root dentry.

This leads to an oops looking like:

	general protection fault, ...
	KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f]
	...
	RIP: 0010:afs_dynroot_depopulate+0x25f/0x529 fs/afs/dynroot.c:385
	...
	Call Trace:
	 afs_kill_super+0x13b/0x180 fs/afs/super.c:535
	 deactivate_locked_super+0x94/0x160 fs/super.c:335
	 afs_get_tree+0x1124/0x1460 fs/afs/super.c:598
	 vfs_get_tree+0x89/0x2f0 fs/super.c:1547
	 do_new_mount fs/namespace.c:2875 [inline]
	 path_mount+0x1387/0x2070 fs/namespace.c:3192
	 do_mount fs/namespace.c:3205 [inline]
	 __do_sys_mount fs/namespace.c:3413 [inline]
	 __se_sys_mount fs/namespace.c:3390 [inline]
	 __x64_sys_mount+0x27f/0x300 fs/namespace.c:3390
	 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
	 entry_SYSCALL_64_after_hwframe+0x44/0xa9

which is oopsing on this line:

	inode_lock(root->d_inode);

presumably because sb->s_root was NULL.

Fixes: 0da0b7fd73 ("afs: Display manually added cells in dynamic root mount")
Reported-by: syzbot+c1eff8205244ae7e11a6@syzkaller.appspotmail.com
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
 		2020-08-26 10:41:05 +02:00
..
Kconfig
…
Makefile
…
addr_list.c
…
afs.h
…
afs_cm.h
…
afs_fs.h
…
afs_vl.h
…
cache.c
…
callback.c
…
cell.c afs: Fix storage of cell names 2020-06-30 15:37:02 -04:00
cmservice.c afs: Fix to actually set AFS_SERVER_FL_HAVE_EPOCH 2020-05-02 08:48:43 +02:00
dir.c afs: Always include dir in bulk status fetch from afs_do_lookup() 2020-06-24 17:50:46 +02:00
dir_edit.c
…
dir_silly.c afs: Fix race between post-modification dir edit and readdir/d_revalidate 2020-04-23 10:36:25 +02:00
dynroot.c afs: Fix NULL deref in afs_dynroot_depopulate() 2020-08-26 10:41:05 +02:00
file.c
…
flock.c
…
fs_probe.c rxrpc: Fix the excessive initial retransmission timeout 2020-05-27 17:46:48 +02:00
fsclient.c afs: Set error flag rather than return error from file status decode 2020-06-24 17:50:46 +02:00
inode.c afs: Fix EOF corruption 2020-06-24 17:50:46 +02:00
internal.h afs: Fix storage of cell names 2020-06-30 15:37:02 -04:00
main.c
…
misc.c afs: Fix the mapping of the UAEOVERFLOW abort code 2020-06-24 17:50:46 +02:00
mntpt.c
…
proc.c afs: Fix memory leak in afs_put_sysnames() 2020-06-24 17:50:42 +02:00
protocol_uae.h
…
protocol_yfs.h
…
rotate.c afs: Make record checking use TASK_UNINTERRUPTIBLE when appropriate 2020-05-02 08:48:43 +02:00
rxrpc.c afs: Set error flag rather than return error from file status decode 2020-06-24 17:50:46 +02:00
security.c
…
server.c afs: Make record checking use TASK_UNINTERRUPTIBLE when appropriate 2020-05-02 08:48:43 +02:00
server_list.c
…
super.c
…
vl_list.c
…
vl_probe.c rxrpc: Fix the excessive initial retransmission timeout 2020-05-27 17:46:48 +02:00
vl_rotate.c
…
vlclient.c
…
volume.c afs: Make record checking use TASK_UNINTERRUPTIBLE when appropriate 2020-05-02 08:48:43 +02:00
write.c afs: afs_write_end() should change i_size under the right lock 2020-06-24 17:50:46 +02:00
xattr.c
…
xdr_fs.h
…
yfsclient.c afs: Set error flag rather than return error from file status decode 2020-06-24 17:50:46 +02:00