It's trivial to trigger a use-after-free bug in the ocfs2 quotas code using
fstest generic/452. After a read-only remount, quotas are suspended and
ocfs2_mem_dqinfo is freed through ->ocfs2_local_free_info(). When unmounting
the filesystem, an UAF access to the oinfo will eventually cause a crash.
BUG: KASAN: slab-use-after-free in timer_delete+0x54/0xc0
Read of size 8 at addr ffff8880389a8208 by task umount/669
...
Call Trace:
<TASK>
...
timer_delete+0x54/0xc0
try_to_grab_pending+0x31/0x230
__cancel_work_timer+0x6c/0x270
ocfs2_disable_quotas.isra.0+0x3e/0xf0 [ocfs2]
ocfs2_dismount_volume+0xdd/0x450 [ocfs2]
generic_shutdown_super+0xaa/0x280
kill_block_super+0x46/0x70
deactivate_locked_super+0x4d/0xb0
cleanup_mnt+0x135/0x1f0
...
</TASK>
Allocated by task 632:
kasan_save_stack+0x1c/0x40
kasan_set_track+0x21/0x30
__kasan_kmalloc+0x8b/0x90
ocfs2_local_read_info+0xe3/0x9a0 [ocfs2]
dquot_load_quota_sb+0x34b/0x680
dquot_load_quota_inode+0xfe/0x1a0
ocfs2_enable_quotas+0x190/0x2f0 [ocfs2]
ocfs2_fill_super+0x14ef/0x2120 [ocfs2]
mount_bdev+0x1be/0x200
legacy_get_tree+0x6c/0xb0
vfs_get_tree+0x3e/0x110
path_mount+0xa90/0xe10
__x64_sys_mount+0x16f/0x1a0
do_syscall_64+0x43/0x90
entry_SYSCALL_64_after_hwframe+0x72/0xdc
Freed by task 650:
kasan_save_stack+0x1c/0x40
kasan_set_track+0x21/0x30
kasan_save_free_info+0x2a/0x50
__kasan_slab_free+0xf9/0x150
__kmem_cache_free+0x89/0x180
ocfs2_local_free_info+0x2ba/0x3f0 [ocfs2]
dquot_disable+0x35f/0xa70
ocfs2_susp_quotas.isra.0+0x159/0x1a0 [ocfs2]
ocfs2_remount+0x150/0x580 [ocfs2]
reconfigure_super+0x1a5/0x3a0
path_mount+0xc8a/0xe10
__x64_sys_mount+0x16f/0x1a0
do_syscall_64+0x43/0x90
entry_SYSCALL_64_after_hwframe+0x72/0xdc
Cc: <[email protected]>
Signed-off-by: Luís Henriques <[email protected]>
---
Changes since v1:
- Fixed changelog to explicitly state 'read-only remount'
- Added KASAN splat to changelog
fs/ocfs2/super.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
index 0b0e6a132101..988d1c076861 100644
--- a/fs/ocfs2/super.c
+++ b/fs/ocfs2/super.c
@@ -952,8 +952,10 @@ static void ocfs2_disable_quotas(struct ocfs2_super *osb)
for (type = 0; type < OCFS2_MAXQUOTAS; type++) {
if (!sb_has_quota_loaded(sb, type))
continue;
- oinfo = sb_dqinfo(sb, type)->dqi_priv;
- cancel_delayed_work_sync(&oinfo->dqi_sync_work);
+ if (!sb_has_quota_suspended(sb, type)) {
+ oinfo = sb_dqinfo(sb, type)->dqi_priv;
+ cancel_delayed_work_sync(&oinfo->dqi_sync_work);
+ }
inode = igrab(sb->s_dquot.files[type]);
/* Turn off quotas. This will remove all dquot structures from
* memory and so they will be automatically synced to global
On 5/23/23 5:33 PM, Luís Henriques wrote:
> It's trivial to trigger a use-after-free bug in the ocfs2 quotas code using
> fstest generic/452. After a read-only remount, quotas are suspended and
> ocfs2_mem_dqinfo is freed through ->ocfs2_local_free_info(). When unmounting
> the filesystem, an UAF access to the oinfo will eventually cause a crash.
>
> BUG: KASAN: slab-use-after-free in timer_delete+0x54/0xc0
> Read of size 8 at addr ffff8880389a8208 by task umount/669
> ...
> Call Trace:
> <TASK>
> ...
> timer_delete+0x54/0xc0
> try_to_grab_pending+0x31/0x230
> __cancel_work_timer+0x6c/0x270
> ocfs2_disable_quotas.isra.0+0x3e/0xf0 [ocfs2]
> ocfs2_dismount_volume+0xdd/0x450 [ocfs2]
> generic_shutdown_super+0xaa/0x280
> kill_block_super+0x46/0x70
> deactivate_locked_super+0x4d/0xb0
> cleanup_mnt+0x135/0x1f0
> ...
> </TASK>
>
> Allocated by task 632:
> kasan_save_stack+0x1c/0x40
> kasan_set_track+0x21/0x30
> __kasan_kmalloc+0x8b/0x90
> ocfs2_local_read_info+0xe3/0x9a0 [ocfs2]
> dquot_load_quota_sb+0x34b/0x680
> dquot_load_quota_inode+0xfe/0x1a0
> ocfs2_enable_quotas+0x190/0x2f0 [ocfs2]
> ocfs2_fill_super+0x14ef/0x2120 [ocfs2]
> mount_bdev+0x1be/0x200
> legacy_get_tree+0x6c/0xb0
> vfs_get_tree+0x3e/0x110
> path_mount+0xa90/0xe10
> __x64_sys_mount+0x16f/0x1a0
> do_syscall_64+0x43/0x90
> entry_SYSCALL_64_after_hwframe+0x72/0xdc
>
> Freed by task 650:
> kasan_save_stack+0x1c/0x40
> kasan_set_track+0x21/0x30
> kasan_save_free_info+0x2a/0x50
> __kasan_slab_free+0xf9/0x150
> __kmem_cache_free+0x89/0x180
> ocfs2_local_free_info+0x2ba/0x3f0 [ocfs2]
> dquot_disable+0x35f/0xa70
> ocfs2_susp_quotas.isra.0+0x159/0x1a0 [ocfs2]
> ocfs2_remount+0x150/0x580 [ocfs2]
> reconfigure_super+0x1a5/0x3a0
> path_mount+0xc8a/0xe10
> __x64_sys_mount+0x16f/0x1a0
> do_syscall_64+0x43/0x90
> entry_SYSCALL_64_after_hwframe+0x72/0xdc
>
> Cc: <[email protected]>
> Signed-off-by: Luís Henriques <[email protected]>
Reviewed-by: Joseph Qi <[email protected]>
Tested-by: Joseph Qi <[email protected]>
Tested with following procedures:
mkfs.ocfs2 -b 4k -C 1M -N 2 --fs-features=usrquota,grpquota /dev/vdc
/etc/init.d/o2cb.init online ocfs2cluster
mount.ocfs2 -o usrquota,grpquota /dev/vdc /mnt/ocfs2
mount.ocfs2 -o remount,ro,heartbeat=local /dev/vdc /mnt/ocfs2
umount /mnt/ocfs2
> ---
> Changes since v1:
> - Fixed changelog to explicitly state 'read-only remount'
> - Added KASAN splat to changelog
>
> fs/ocfs2/super.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
> index 0b0e6a132101..988d1c076861 100644
> --- a/fs/ocfs2/super.c
> +++ b/fs/ocfs2/super.c
> @@ -952,8 +952,10 @@ static void ocfs2_disable_quotas(struct ocfs2_super *osb)
> for (type = 0; type < OCFS2_MAXQUOTAS; type++) {
> if (!sb_has_quota_loaded(sb, type))
> continue;
> - oinfo = sb_dqinfo(sb, type)->dqi_priv;
> - cancel_delayed_work_sync(&oinfo->dqi_sync_work);
> + if (!sb_has_quota_suspended(sb, type)) {
> + oinfo = sb_dqinfo(sb, type)->dqi_priv;
> + cancel_delayed_work_sync(&oinfo->dqi_sync_work);
> + }
> inode = igrab(sb->s_dquot.files[type]);
> /* Turn off quotas. This will remove all dquot structures from
> * memory and so they will be automatically synced to global