linux-ext4 - [PATCH] ext2: replace BUG_ON with WARN_ON_ONCE in ext2_get

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Message-ID: <20260207010617.216675-1-nikic.milos@gmail.com>
Date: Fri,  6 Feb 2026 17:06:17 -0800
From: Milos Nikic <nikic.milos@...il.com>
To: jack@...e.com
Cc: linux-ext4@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Milos Nikic <nikic.milos@...il.com>
Subject: [PATCH] ext2: replace BUG_ON with WARN_ON_ONCE in ext2_get_blocks

If ext2_get_blocks() is called with maxblocks == 0, it currently triggers
a BUG_ON(), causing a kernel panic.

While this condition implies a logic error in the caller, a filesystem
should not crash the system due to invalid arguments.

Replace the BUG_ON() with a WARN_ON_ONCE() to provide a stack trace for
debugging, and return -EINVAL to handle the error gracefully.

Signed-off-by: Milos Nikic <nikic.milos@...il.com>
---
 fs/ext2/inode.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index dbfe9098a124..18bf1a91dbc2 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -638,7 +638,8 @@ static int ext2_get_blocks(struct inode *inode,
 	int count = 0;
 	ext2_fsblk_t first_block = 0;
 
-	BUG_ON(maxblocks == 0);
+	if (WARN_ON_ONCE(maxblocks == 0))
+		return -EINVAL;
 
 	depth = ext2_block_to_path(inode,iblock,offsets,&blocks_to_boundary);
 
-- 
2.52.0