[PATCH AUTOSEL 6.6 096/139] jfs: Fix uaf in dbFreeBits

Sasha Levin
2024-09-25T12:16:03Z

From: Edward Adam Davis <eadavis@qq.com>

[ Upstream commit d6c1b3599b2feb5c7291f5ac3a36e5fa7cedb234 ]

[syzbot reported]
==================================================================
BUG: KASAN: slab-use-after-free in __mutex_lock_common kernel/locking/mutex.c:587 [inline]
BUG: KASAN: slab-use-after-free in __mutex_lock+0xfe/0xd70 kernel/locking/mutex.c:752
Read of size 8 at addr ffff8880229254b0 by task syz-executor357/5216

CPU: 0 UID: 0 PID: 5216 Comm: syz-executor357 Not tainted 6.11.0-rc3-syzkaller-00156-gd7a5aa4b3c00 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:93 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:119
print_address_description mm/kasan/report.c:377 [inline]
print_report+0x169/0x550 mm/kasan/report.c:488
kasan_report+0x143/0x180 mm/kasan/report.c:601
__mutex_lock_common kernel/locking/mutex.c:587 [inline]
__mutex_lock+0xfe/0xd70 kernel/locking/mutex.c:752
dbFreeBits+0x7ea/0xd90 fs/jfs/jfs_dmap.c:2390
dbFreeDmap fs/jfs/jfs_dmap.c:2089 [inline]
dbFree+0x35b/0x680 fs/jfs/jfs_dmap.c:409
dbDiscardAG+0x8a9/0xa20 fs/jfs/jfs_dmap.c:1650
jfs_ioc_trim+0x433/0x670 fs/jfs/jfs_discard.c:100
jfs_ioctl+0x2d0/0x3e0 fs/jfs/ioctl.c:131
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:907 [inline]
__se_sys_ioctl+0xfc/0x170 fs/ioctl.c:893
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83

Freed by task 5218:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:579
poison_slab_object+0xe0/0x150 mm/kasan/common.c:240
__kasan_slab_free+0x37/0x60 mm/kasan/common.c:256
kasan_slab_free include/linux/kasan.h:184 [inline]
slab_free_hook mm/slub.c:2252 [inline]
slab_free mm/slub.c:4473 [inline]
kfree+0x149/0x360 mm/slub.c:4594
dbUnmount+0x11d/0x190 fs/jfs/jfs_dmap.c:278
jfs_mount_rw+0x4ac/0x6a0 fs/jfs/jfs_mount.c:247
jfs_remount+0x3d1/0x6b0 fs/jfs/super.c:454
reconfigure_super+0x445/0x880 fs/super.c:1083
vfs_cmd_reconfigure fs/fsopen.c:263 [inline]
vfs_fsconfig_locked fs/fsopen.c:292 [inline]
__do_sys_fsconfig fs/fsopen.c:473 [inline]
__se_sys_fsconfig+0xb6e/0xf80 fs/fsopen.c:345
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

[Analysis]
There are two paths (dbUnmount and jfs_ioc_trim) that generate race
condition when accessing bmap, which leads to the occurrence of uaf.

Use the lock s_umount to synchronize them, in order to avoid uaf caused
by race condition.

Reported-and-tested-by: syzbot+3c010e21296f33a5dc16@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/jfs/jfs_discard.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/fs/jfs/jfs_discard.c b/fs/jfs/jfs_discard.c
index 575cb2ba74fc8..5f4b305030ad5 100644
--- a/fs/jfs/jfs_discard.c
+++ b/fs/jfs/jfs_discard.c
@@ -65,7 +65,7 @@ void jfs_issue_discard(struct inode *ip, u64 blkno, u64 nblocks)
int jfs_ioc_trim(struct inode *ip, struct fstrim_range *range)
{
struct inode *ipbmap = JFS_SBI(ip->i_sb)->ipbmap;
- struct bmap *bmp = JFS_SBI(ip->i_sb)->bmap;
+ struct bmap *bmp;
struct super_block *sb = ipbmap->i_sb;
int agno, agno_end;
u64 start, end, minlen;
@@ -83,10 +83,15 @@ int jfs_ioc_trim(struct inode *ip, struct fstrim_range *range)
if (minlen == 0)
minlen = 1;

+ down_read(&sb->s_umount);
+ bmp = JFS_SBI(ip->i_sb)->bmap;
+
if (minlen > bmp->db_agsize ||
start >= bmp->db_mapsize ||
- range->len < sb->s_blocksize)
+ range->len < sb->s_blocksize) {
+ up_read(&sb->s_umount);
return -EINVAL;
+ }

if (end >= bmp->db_mapsize)
end = bmp->db_mapsize - 1;
@@ -100,6 +105,8 @@ int jfs_ioc_trim(struct inode *ip, struct fstrim_range *range)
trimmed += dbDiscardAG(ip, agno, minlen);
agno++;
}
+
+ up_read(&sb->s_umount);
range->len = trimmed << sb->s_blocksize_bits;

return 0;
--
2.43.0