Re: [PATCH] xfs: fix array bounds checking in log recovery

[Hongling Zeng <zhongling0719@126.com>]

在 2026年09月01日 15:06, Carlos Maiolino 写道:
> On Mon, Aug 24, 2026 at 05:45:35PM +0800, Hongling Zeng wrote:
>> The log recovery code increments array indices based on bits set in
>> blf_data_map without verifying that the indices stay within the bounds
>> of the item->ri_buf array.
>>
>> Since blf_data_map is from untrusted log data, a malicious log could set
>> many bits while ri_total is small, causing array index overflow.
>>
>> This can result in an out-of-bounds access during log recovery, causing
>> a kernel crash or memory corruption.
>>
>> This patch adds array bounds checking for ri_buf access in
>> xlog_recover_do_reg_buffer() and xlog_recover_do_inode_buffer().
>>
>> The check in xlog_recover_do_inode_buffer() is placed right before the
>> actual array access, not after incrementing the index, to avoid false
>> positives when processing the last valid region.
>>
>> Fixes: 1094d3f12363 ("xfs: refactor log recovery buffer item dispatch for pass2 commit functions")
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Hongling Zeng <zenghongling@kylinos.cn>
> Hi,
>
> is this a re-send? A v2? Please specify why you are sending the same
> patche again. This saves a lot of time trying to understand why there
> are two patches with the same subject in the list.
Hi ,
This is the same patch version, but the previous submission failed to
apply because my local repository was out of date. I updated my tree and
resubmitted the patch with the same fix.

Sorry for the confusion.

Thanks,
Hongling
>> ---
>>   fs/xfs/xfs_buf_item_recover.c | 26 ++++++++++++++++++++++++++
>>   1 file changed, 26 insertions(+)
>>
>> diff --git a/fs/xfs/xfs_buf_item_recover.c b/fs/xfs/xfs_buf_item_recover.c
>> index 57929f115055..7148716366ba 100644
>> --- a/fs/xfs/xfs_buf_item_recover.c
>> +++ b/fs/xfs/xfs_buf_item_recover.c
>> @@ -485,6 +485,19 @@ xlog_recover_do_reg_buffer(
>>   			break;
>>   		nbits = xfs_contig_bits(buf_f->blf_data_map,
>>   					buf_f->blf_map_size, bit);
>> +
>> +		/*
>> +		 * The bitmap can have more bits set than there are regions
>> +		 * in ri_buf, so we must check array bounds before using the
>> +		 * index to access ri_buf[i].
>> +		 */
>> +		if (XFS_IS_CORRUPT(mp, i >= item->ri_total)) {
>> +			xfs_alert(mp,
>> +		"Buffer log item index (%d) exceeds allocated regions (%d).",
>> +					i, item->ri_total);
>> +			return -EFSCORRUPTED;
>> +		}
>> +
>>   		ASSERT(nbits > 0);
>>   		ASSERT(item->ri_buf[i].iov_base != NULL);
>>   		ASSERT(item->ri_buf[i].iov_len % XFS_BLF_CHUNK == 0);
>> @@ -688,6 +701,19 @@ xlog_recover_do_inode_buffer(
>>   		if (next_unlinked_offset < reg_buf_offset)
>>   			continue;
>>   
>> +		/*
>> +		 * Check array bounds here (right before accessing ri_buf)
>> +		 * rather than after incrementing item_index. This avoids
>> +		 * incorrectly rejecting logs when item_index reaches
>> +		 * ri_total after processing the final valid region.
>> +		 */
>> +		if (XFS_IS_CORRUPT(mp, item_index >= item->ri_total)) {
>> +			xfs_alert(mp,
>> +		"Inode buffer log item index (%d) exceeds allocated regions (%d).",
>> +				item_index, item->ri_total);
>> +			return -EFSCORRUPTED;
>> +		}
>> +
>>   		ASSERT(item->ri_buf[item_index].iov_base != NULL);
>>   		ASSERT((item->ri_buf[item_index].iov_len % XFS_BLF_CHUNK) == 0);
>>   		ASSERT((reg_buf_offset + reg_buf_bytes) <= BBTOB(bp->b_length));
>> -- 
>> 2.25.1
>>
>>