* [PATCH] ext4: reject mount if bigalloc with s_first_data_block != 0
@ 2026-03-17 14:23 Helen Koike
0 siblings, 0 replies; only message in thread
From: Helen Koike @ 2026-03-17 14:23 UTC (permalink / raw)
To: tytso, adilger.kernel, linux-ext4, linux-fsdevel, linux-kernel,
kernel-dev, koike, syzbot+b73703b873a33d8eb8f6
bigalloc with s_first_data_block != 0 is not supported, reject mounting
it.
Signed-off-by: Helen Koike <koike@igalia.com>
Suggested-by: Theodore Ts'o <tytso@mit.edu>
Reported-by: syzbot+b73703b873a33d8eb8f6@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=b73703b873a33d8eb8f6
---
fs/ext4/super.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 495f99c10085..9f0cc29b718f 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3626,6 +3626,13 @@ int ext4_feature_set_ok(struct super_block *sb, int readonly)
"extents feature\n");
return 0;
}
+ if (ext4_has_feature_bigalloc(sb) &&
+ le32_to_cpu(EXT4_SB(sb)->s_es->s_first_data_block)) {
+ ext4_msg(sb, KERN_WARNING,
+ "bad geometry: bigalloc file system with non-zero "
+ "first_data_block\n");
+ return 0;
+ }
#if !IS_ENABLED(CONFIG_QUOTA) || !IS_ENABLED(CONFIG_QFMT_V2)
if (!readonly && (ext4_has_feature_quota(sb) ||
--
2.53.0
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