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>
---
Change in v2:
 -Rebase top of for-next and re-send.
---
 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