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[PATCH] ocfs2: fix out-of-bounds write in ocfs2_write_end_inline

Joseph Qi posted 1 patch 2 months, 1 week ago 
fs/ocfs2/inode.c | 10 ++++++++++
1 file changed, 10 insertions(+)
[PATCH] ocfs2: fix out-of-bounds write in ocfs2_write_end_inline
Posted by Joseph Qi 2 months, 1 week ago 
KASAN reports a use-after-free write of 4086 bytes in
ocfs2_write_end_inline, called from ocfs2_write_end_nolock during a
copy_file_range splice fallback on a corrupted ocfs2 filesystem mounted
on a loop device. The actual bug is an out-of-bounds write past the
inode block buffer, not a true use-after-free. The write overflows into
an adjacent freed page, which KASAN reports as UAF.

The root cause is that ocfs2_try_to_write_inline_data trusts the
on-disk id_count field to determine whether a write fits in inline
data. On a corrupted filesystem, id_count can exceed the physical
maximum inline data capacity, causing writes to overflow the inode
block buffer.

Call trace (crash path):

   vfs_copy_file_range (fs/read_write.c:1634)
     do_splice_direct
       splice_direct_to_actor
         iter_file_splice_write
           ocfs2_file_write_iter
             generic_perform_write
               ocfs2_write_end
                 ocfs2_write_end_nolock (fs/ocfs2/aops.c:1949)
                   ocfs2_write_end_inline (fs/ocfs2/aops.c:1915)
                     memcpy_from_folio     <-- KASAN: write OOB

So add id_count upper bound check in ocfs2_validate_inode_block() to
alongside the existing i_size check to fix it.

Reported-by: syzbot+62c1793956716ea8b28a@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=62c1793956716ea8b28a
Cc: <stable@vger.kernel.org>
Signed-off-by: Joseph Qi <joseph.qi@linux.alibaba.com>
---
 fs/ocfs2/inode.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
index 03a51662ea8e..a2ccd8011706 100644
--- a/fs/ocfs2/inode.c
+++ b/fs/ocfs2/inode.c
@@ -1505,6 +1505,16 @@ int ocfs2_validate_inode_block(struct super_block *sb,
 			goto bail;
 		}
 
+		if (le16_to_cpu(data->id_count) >
+		    ocfs2_max_inline_data_with_xattr(sb, di)) {
+			rc = ocfs2_error(sb,
+					 "Invalid dinode #%llu: inline data id_count %u exceeds max %d\n",
+					 (unsigned long long)bh->b_blocknr,
+					 le16_to_cpu(data->id_count),
+					 ocfs2_max_inline_data_with_xattr(sb, di));
+			goto bail;
+		}
+
 		if (le64_to_cpu(di->i_size) > le16_to_cpu(data->id_count)) {
 			rc = ocfs2_error(sb,
 					 "Invalid dinode #%llu: inline data i_size %llu exceeds id_count %u\n",
-- 
2.39.3
Re: [PATCH] ocfs2: fix out-of-bounds write in ocfs2_write_end_inline
Posted by Heming Zhao 2 months, 1 week ago 
On Fri, Apr 03, 2026 at 02:38:30PM +0800, Joseph Qi wrote:
> KASAN reports a use-after-free write of 4086 bytes in
> ocfs2_write_end_inline, called from ocfs2_write_end_nolock during a
> copy_file_range splice fallback on a corrupted ocfs2 filesystem mounted
> on a loop device. The actual bug is an out-of-bounds write past the
> inode block buffer, not a true use-after-free. The write overflows into
> an adjacent freed page, which KASAN reports as UAF.
> 
> The root cause is that ocfs2_try_to_write_inline_data trusts the
> on-disk id_count field to determine whether a write fits in inline
> data. On a corrupted filesystem, id_count can exceed the physical
> maximum inline data capacity, causing writes to overflow the inode
> block buffer.
> 
> Call trace (crash path):
> 
>    vfs_copy_file_range (fs/read_write.c:1634)
>      do_splice_direct
>        splice_direct_to_actor
>          iter_file_splice_write
>            ocfs2_file_write_iter
>              generic_perform_write
>                ocfs2_write_end
>                  ocfs2_write_end_nolock (fs/ocfs2/aops.c:1949)
>                    ocfs2_write_end_inline (fs/ocfs2/aops.c:1915)
>                      memcpy_from_folio     <-- KASAN: write OOB
> 
> So add id_count upper bound check in ocfs2_validate_inode_block() to
> alongside the existing i_size check to fix it.
> 
> Reported-by: syzbot+62c1793956716ea8b28a@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=62c1793956716ea8b28a
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Joseph Qi <joseph.qi@linux.alibaba.com>

Looks good to me.
Reviewed-by: Heming Zhao <heming.zhao@suse.com>
> ---
>  fs/ocfs2/inode.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
> index 03a51662ea8e..a2ccd8011706 100644
> --- a/fs/ocfs2/inode.c
> +++ b/fs/ocfs2/inode.c
> @@ -1505,6 +1505,16 @@ int ocfs2_validate_inode_block(struct super_block *sb,
>  			goto bail;
>  		}
>  
> +		if (le16_to_cpu(data->id_count) >
> +		    ocfs2_max_inline_data_with_xattr(sb, di)) {
> +			rc = ocfs2_error(sb,
> +					 "Invalid dinode #%llu: inline data id_count %u exceeds max %d\n",
> +					 (unsigned long long)bh->b_blocknr,
> +					 le16_to_cpu(data->id_count),
> +					 ocfs2_max_inline_data_with_xattr(sb, di));
> +			goto bail;
> +		}
> +
>  		if (le64_to_cpu(di->i_size) > le16_to_cpu(data->id_count)) {
>  			rc = ocfs2_error(sb,
>  					 "Invalid dinode #%llu: inline data i_size %llu exceeds id_count %u\n",
> -- 
> 2.39.3
>
Re: [PATCH] ocfs2: fix out-of-bounds write in ocfs2_write_end_inline
Posted by Andrew Morton 2 months, 1 week ago 
On Fri,  3 Apr 2026 14:38:30 +0800 Joseph Qi <joseph.qi@linux.alibaba.com> wrote:

> KASAN reports a use-after-free write of 4086 bytes in
> ocfs2_write_end_inline, called from ocfs2_write_end_nolock during a
> copy_file_range splice fallback on a corrupted ocfs2 filesystem mounted
> on a loop device. The actual bug is an out-of-bounds write past the
> inode block buffer, not a true use-after-free. The write overflows into
> an adjacent freed page, which KASAN reports as UAF.
> 
> The root cause is that ocfs2_try_to_write_inline_data trusts the
> on-disk id_count field to determine whether a write fits in inline
> data. On a corrupted filesystem, id_count can exceed the physical
> maximum inline data capacity, causing writes to overflow the inode
> block buffer.
> 
> Call trace (crash path):
> 
>    vfs_copy_file_range (fs/read_write.c:1634)
>      do_splice_direct
>        splice_direct_to_actor
>          iter_file_splice_write
>            ocfs2_file_write_iter
>              generic_perform_write
>                ocfs2_write_end
>                  ocfs2_write_end_nolock (fs/ocfs2/aops.c:1949)
>                    ocfs2_write_end_inline (fs/ocfs2/aops.c:1915)
>                      memcpy_from_folio     <-- KASAN: write OOB
> 
> So add id_count upper bound check in ocfs2_validate_inode_block() to
> alongside the existing i_size check to fix it.

AI review had a question:
	https://sashiko.dev/#/patchset/20260403063830.3662739-1-joseph.qi@linux.alibaba.com
Re: [PATCH] ocfs2: fix out-of-bounds write in ocfs2_write_end_inline
Posted by Joseph Qi 2 months, 1 week ago 

On 4/4/26 3:28 AM, Andrew Morton wrote:
> On Fri,  3 Apr 2026 14:38:30 +0800 Joseph Qi <joseph.qi@linux.alibaba.com> wrote:
> 
>> KASAN reports a use-after-free write of 4086 bytes in
>> ocfs2_write_end_inline, called from ocfs2_write_end_nolock during a
>> copy_file_range splice fallback on a corrupted ocfs2 filesystem mounted
>> on a loop device. The actual bug is an out-of-bounds write past the
>> inode block buffer, not a true use-after-free. The write overflows into
>> an adjacent freed page, which KASAN reports as UAF.
>>
>> The root cause is that ocfs2_try_to_write_inline_data trusts the
>> on-disk id_count field to determine whether a write fits in inline
>> data. On a corrupted filesystem, id_count can exceed the physical
>> maximum inline data capacity, causing writes to overflow the inode
>> block buffer.
>>
>> Call trace (crash path):
>>
>>    vfs_copy_file_range (fs/read_write.c:1634)
>>      do_splice_direct
>>        splice_direct_to_actor
>>          iter_file_splice_write
>>            ocfs2_file_write_iter
>>              generic_perform_write
>>                ocfs2_write_end
>>                  ocfs2_write_end_nolock (fs/ocfs2/aops.c:1949)
>>                    ocfs2_write_end_inline (fs/ocfs2/aops.c:1915)
>>                      memcpy_from_folio     <-- KASAN: write OOB
>>
>> So add id_count upper bound check in ocfs2_validate_inode_block() to
>> alongside the existing i_size check to fix it.
> 
> AI review had a question:
> 	https://sashiko.dev/#/patchset/20260403063830.3662739-1-joseph.qi@linux.alibaba.com

Sashiko worries about it can't handle the case OCFS2_INLINE_DATA_FL not set.
I think it is a seprated case.

Thanks,
Joseph
Re: [PATCH] ocfs2: fix out-of-bounds write in ocfs2_write_end_inline
Posted by Andrew Morton 2 months, 1 week ago 
On Fri,  3 Apr 2026 14:38:30 +0800 Joseph Qi <joseph.qi@linux.alibaba.com> wrote:

> KASAN reports a use-after-free write of 4086 bytes in
> ocfs2_write_end_inline, called from ocfs2_write_end_nolock during a
> copy_file_range splice fallback on a corrupted ocfs2 filesystem mounted
> on a loop device. The actual bug is an out-of-bounds write past the
> inode block buffer, not a true use-after-free. The write overflows into
> an adjacent freed page, which KASAN reports as UAF.
> 
> The root cause is that ocfs2_try_to_write_inline_data trusts the
> on-disk id_count field to determine whether a write fits in inline
> data. On a corrupted filesystem, id_count can exceed the physical
> maximum inline data capacity, causing writes to overflow the inode
> block buffer.
> 
> Call trace (crash path):
> 
>    vfs_copy_file_range (fs/read_write.c:1634)
>      do_splice_direct
>        splice_direct_to_actor
>          iter_file_splice_write
>            ocfs2_file_write_iter
>              generic_perform_write
>                ocfs2_write_end
>                  ocfs2_write_end_nolock (fs/ocfs2/aops.c:1949)
>                    ocfs2_write_end_inline (fs/ocfs2/aops.c:1915)
>                      memcpy_from_folio     <-- KASAN: write OOB
> 
> So add id_count upper bound check in ocfs2_validate_inode_block() to
> alongside the existing i_size check to fix it.

Thanks.

> --- a/fs/ocfs2/inode.c
> +++ b/fs/ocfs2/inode.c
> @@ -1505,6 +1505,16 @@ int ocfs2_validate_inode_block(struct super_block *sb,
>  			goto bail;
>  		}
>  
> +		if (le16_to_cpu(data->id_count) >
> +		    ocfs2_max_inline_data_with_xattr(sb, di)) {
> +			rc = ocfs2_error(sb,
> +					 "Invalid dinode #%llu: inline data id_count %u exceeds max %d\n",
> +					 (unsigned long long)bh->b_blocknr,
> +					 le16_to_cpu(data->id_count),
> +					 ocfs2_max_inline_data_with_xattr(sb, di));
> +			goto bail;
> +		}
> +
>  		if (le64_to_cpu(di->i_size) > le16_to_cpu(data->id_count)) {
>  			rc = ocfs2_error(sb,
>  					 "Invalid dinode #%llu: inline data i_size %llu exceeds id_count %u\n",

Even though the surrounding code is from 2025 (1524af3685b35), I think
this bug predates 1524af3685b35?

If so, I expect the -stable people will have trouble backporting this. 
If so, they'll report it and shall ask for a reworked version.
Re: [PATCH] ocfs2: fix out-of-bounds write in ocfs2_write_end_inline
Posted by Joseph Qi 2 months, 1 week ago 

On 4/3/26 2:48 PM, Andrew Morton wrote:
> On Fri,  3 Apr 2026 14:38:30 +0800 Joseph Qi <joseph.qi@linux.alibaba.com> wrote:
> 
>> KASAN reports a use-after-free write of 4086 bytes in
>> ocfs2_write_end_inline, called from ocfs2_write_end_nolock during a
>> copy_file_range splice fallback on a corrupted ocfs2 filesystem mounted
>> on a loop device. The actual bug is an out-of-bounds write past the
>> inode block buffer, not a true use-after-free. The write overflows into
>> an adjacent freed page, which KASAN reports as UAF.
>>
>> The root cause is that ocfs2_try_to_write_inline_data trusts the
>> on-disk id_count field to determine whether a write fits in inline
>> data. On a corrupted filesystem, id_count can exceed the physical
>> maximum inline data capacity, causing writes to overflow the inode
>> block buffer.
>>
>> Call trace (crash path):
>>
>>    vfs_copy_file_range (fs/read_write.c:1634)
>>      do_splice_direct
>>        splice_direct_to_actor
>>          iter_file_splice_write
>>            ocfs2_file_write_iter
>>              generic_perform_write
>>                ocfs2_write_end
>>                  ocfs2_write_end_nolock (fs/ocfs2/aops.c:1949)
>>                    ocfs2_write_end_inline (fs/ocfs2/aops.c:1915)
>>                      memcpy_from_folio     <-- KASAN: write OOB
>>
>> So add id_count upper bound check in ocfs2_validate_inode_block() to
>> alongside the existing i_size check to fix it.
> 
> Thanks.
> 
>> --- a/fs/ocfs2/inode.c
>> +++ b/fs/ocfs2/inode.c
>> @@ -1505,6 +1505,16 @@ int ocfs2_validate_inode_block(struct super_block *sb,
>>  			goto bail;
>>  		}
>>  
>> +		if (le16_to_cpu(data->id_count) >
>> +		    ocfs2_max_inline_data_with_xattr(sb, di)) {
>> +			rc = ocfs2_error(sb,
>> +					 "Invalid dinode #%llu: inline data id_count %u exceeds max %d\n",
>> +					 (unsigned long long)bh->b_blocknr,
>> +					 le16_to_cpu(data->id_count),
>> +					 ocfs2_max_inline_data_with_xattr(sb, di));
>> +			goto bail;
>> +		}
>> +
>>  		if (le64_to_cpu(di->i_size) > le16_to_cpu(data->id_count)) {
>>  			rc = ocfs2_error(sb,
>>  					 "Invalid dinode #%llu: inline data i_size %llu exceeds id_count %u\n",
> 
> Even though the surrounding code is from 2025 (1524af3685b35), I think
> this bug predates 1524af3685b35?
> 
> If so, I expect the -stable people will have trouble backporting this. 
> If so, they'll report it and shall ask for a reworked version.

This seems blame to a very old commit (perhaps 1afc32b95233?), since it
was designed to trust the on-disk block.
So I don't add a fixes tag for it.

Thanks,
Joseph

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