2023-04-10 17:50:07

by Gao Xiang

Subject: [PATCH] erofs: stop parsing non-compact HEAD index if clusterofs is invalid

Syzbot generated a crafted image [1] with a non-compact HEAD index of
clusterofs 33024 while valid numbers should be 0 ~ lclustersize-1,
which causes the following unexpected behavior as below:

BUG: unable to handle page fault for address: fffff52101a3fff9
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 23ffed067 P4D 23ffed067 PUD 0
Oops: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 4398 Comm: kworker/u5:1 Not tainted 6.3.0-rc6-syzkaller-g09a9639e56c0 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023
Workqueue: erofs_worker z_erofs_decompressqueue_work
RIP: 0010:z_erofs_decompress_queue+0xb7e/0x2b40
...
Call Trace:
<TASK>
z_erofs_decompressqueue_work+0x99/0xe0
process_one_work+0x8f6/0x1170
worker_thread+0xa63/0x1210
kthread+0x270/0x300
ret_from_fork+0x1f/0x30

Note that normal images or images using compact indexes are not
impacted. Let's fix this now.

[1] https://lore.kernel.org/r/[email protected]

Reported-by: [email protected]
Fixes: 02827e1796b3 ("staging: erofs: add erofs_map_blocks_iter")
Fixes: 152a333a5895 ("staging: erofs: add compacted compression indexes support")
Signed-off-by: Gao Xiang <[email protected]>
---
fs/erofs/zmap.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c
index cbd3f72c83e9..7ca108c3834c 100644
--- a/fs/erofs/zmap.c
+++ b/fs/erofs/zmap.c
@@ -85,6 +85,10 @@ static int legacy_load_cluster_from_disk(struct z_erofs_maprecorder *m,
if (advise & Z_EROFS_LI_PARTIAL_REF)
m->partialref = true;
m->clusterofs = le16_to_cpu(di->di_clusterofs);
+ if (m->clusterofs >= 1 << vi->z_logical_clusterbits) {
+ DBG_BUGON(1);
+ return -EFSCORRUPTED;
+ }
m->pblk = le32_to_cpu(di->di_u.blkaddr);
break;
default:
--
2.24.4

2023-04-16 14:36:32

by Chao Yu

Subject: Re: [PATCH] erofs: stop parsing non-compact HEAD index if clusterofs is invalid

On 2023/4/11 1:37, Gao Xiang wrote:
> Syzbot generated a crafted image [1] with a non-compact HEAD index of
> clusterofs 33024 while valid numbers should be 0 ~ lclustersize-1,
> which causes the following unexpected behavior as below:
>
> BUG: unable to handle page fault for address: fffff52101a3fff9
> #PF: supervisor read access in kernel mode
> #PF: error_code(0x0000) - not-present page
> PGD 23ffed067 P4D 23ffed067 PUD 0
> Oops: 0000 [#1] PREEMPT SMP KASAN
> CPU: 1 PID: 4398 Comm: kworker/u5:1 Not tainted 6.3.0-rc6-syzkaller-g09a9639e56c0 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023
> Workqueue: erofs_worker z_erofs_decompressqueue_work
> RIP: 0010:z_erofs_decompress_queue+0xb7e/0x2b40
> ...
> Call Trace:
> <TASK>
> z_erofs_decompressqueue_work+0x99/0xe0
> process_one_work+0x8f6/0x1170
> worker_thread+0xa63/0x1210
> kthread+0x270/0x300
> ret_from_fork+0x1f/0x30
>
> Note that normal images or images using compact indexes are not
> impacted. Let's fix this now.
>
> [1] https://lore.kernel.org/r/[email protected]
>
> Reported-by: [email protected]
> Fixes: 02827e1796b3 ("staging: erofs: add erofs_map_blocks_iter")
> Fixes: 152a333a5895 ("staging: erofs: add compacted compression indexes support")
> Signed-off-by: Gao Xiang <[email protected]>

Reviewed-by: Chao Yu <[email protected]>

Thanks,