[PATCH 5.15 462/484] xfs: fix log recovery buffer allocation for the legacy h_size fixup

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5.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Christoph Hellwig <hch@xxxxxx>

commit 45cf976008ddef4a9c9a30310c9b4fb2a9a6602a upstream.

Commit a70f9fe52daa ("xfs: detect and handle invalid iclog size set by
mkfs") added a fixup for incorrect h_size values used for the initial
umount record in old xfsprogs versions.  Later commit 0c771b99d6c9
("xfs: clean up calculation of LR header blocks") cleaned up the log
reover buffer calculation, but stoped using the fixed up h_size value
to size the log recovery buffer, which can lead to an out of bounds
access when the incorrect h_size does not come from the old mkfs
tool, but a fuzzer.

Fix this by open coding xlog_logrec_hblks and taking the fixed h_size
into account for this calculation.

Fixes: 0c771b99d6c9 ("xfs: clean up calculation of LR header blocks")
Reported-by: Sam Sun <samsun1006219@xxxxxxxxx>
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
Reviewed-by: "Darrick J. Wong" <djwong@xxxxxxxxxx>
Signed-off-by: Chandan Babu R <chandanbabu@xxxxxxxxxx>
Signed-off-by: Kevin Berry <kpberry@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 fs/xfs/xfs_log_recover.c |   20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -2972,7 +2972,7 @@ xlog_do_recovery_pass(
 	int			error = 0, h_size, h_len;
 	int			error2 = 0;
 	int			bblks, split_bblks;
-	int			hblks, split_hblks, wrapped_hblks;
+	int			hblks = 1, split_hblks, wrapped_hblks;
 	int			i;
 	struct hlist_head	rhash[XLOG_RHASH_SIZE];
 	LIST_HEAD		(buffer_list);
@@ -3028,14 +3028,22 @@ xlog_do_recovery_pass(
 		if (error)
 			goto bread_err1;
 
-		hblks = xlog_logrec_hblks(log, rhead);
-		if (hblks != 1) {
-			kmem_free(hbp);
-			hbp = xlog_alloc_buffer(log, hblks);
+		/*
+		 * This open codes xlog_logrec_hblks so that we can reuse the
+		 * fixed up h_size value calculated above.  Without that we'd
+		 * still allocate the buffer based on the incorrect on-disk
+		 * size.
+		 */
+		if (h_size > XLOG_HEADER_CYCLE_SIZE &&
+		    (rhead->h_version & cpu_to_be32(XLOG_VERSION_2))) {
+			hblks = DIV_ROUND_UP(h_size, XLOG_HEADER_CYCLE_SIZE);
+			if (hblks > 1) {
+				kmem_free(hbp);
+				hbp = xlog_alloc_buffer(log, hblks);
+			}
 		}
 	} else {
 		ASSERT(log->l_sectBBsize == 1);
-		hblks = 1;
 		hbp = xlog_alloc_buffer(log, 1);
 		h_size = XLOG_BIG_RECORD_BSIZE;
 	}






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