Forwarded: Re: [syzbot] WARNING in rgblk_free (2)

[syzbot <syzbot+3e2c95229d1ab81a0bfd@syzkaller.appspotmail.com>]

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Subject: Re: [syzbot] WARNING in rgblk_free (2)
Author: tristmd@gmail.com

#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

>From b5a6713d34c32c37d273e16bd59099a0a6370de9 Mon Sep 17 00:00:00 2001
From: Tristan Madani <tristan@talencesecurity.com>
Date: Sat, 18 Apr 2026 12:57:17 +0000
Subject: [PATCH] gfs2: replace WARN_ON_ONCE with fs_warn in rgblk_free

rgblk_free() triggers WARN_ON_ONCE when gfs2_rbm_from_block() fails
due to a block number outside the resource group bounds. This can be
triggered by a corrupted filesystem image, causing unnecessary kernel
warnings.

Replace WARN_ON_ONCE with fs_warn() to provide a more informative
diagnostic message while avoiding the kernel warning.

Reported-by: syzbot+3e2c95229d1ab81a0bfd@syzkaller.appspotmail.com
Fixes: 5b924ae2b7b4 ("GFS2: fix rgrp end rounding problem for bsize < page size")
Cc: stable@vger.kernel.org
Signed-off-by: Tristan Madani <tristan@talencesecurity.com>
---
 fs/gfs2/rgrp.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index 26d6c1eea5591..7707c1b1082f8 100644
--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -2266,8 +2266,11 @@ static void rgblk_free(struct gfs2_sbd *sdp, struct gfs2_rgrpd *rgd,
 	struct gfs2_bitmap *bi, *bi_prev = NULL;
 
 	rbm.rgd = rgd;
-	if (WARN_ON_ONCE(gfs2_rbm_from_block(&rbm, bstart)))
+	if (gfs2_rbm_from_block(&rbm, bstart)) {
+		fs_warn(sdp, "rgblk_free: block %llu outside rgrp\n",
+			(unsigned long long)bstart);
 		return;
+	}
 	while (blen--) {
 		bi = rbm_bi(&rbm);
 		if (bi != bi_prev) {
-- 
2.47.3