linux-kernel - [PATCH] block: fix memory leak in __blkdev_issue_zero

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Message-Id: <20251204181259.23864-1-ssrane_b23@ee.vjti.ac.in>
Date: Thu,  4 Dec 2025 23:42:59 +0530
From: Shaurya Rane <ssrane_b23@...vjti.ac.in>
To: axboe@...nel.dk,
	martin.petersen@...cle.com
Cc: linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	skhan@...uxfoundation.org,
	linux-kernel-mentees@...ts.linux.dev,
	david.hunter.linux@...il.com,
	khalid@...nel.org,
	Shaurya Rane <ssrane_b23@...vjti.ac.in>,
	syzbot+527a7e48a3d3d315d862@...kaller.appspotmail.com,
	Keith Busch <kbusch@...nel.org>
Subject: [PATCH] block: fix memory leak in __blkdev_issue_zero_pages

Move the fatal signal check before bio_alloc() to prevent a memory
leak when BLKDEV_ZERO_KILLABLE is set and a fatal signal is pending.

Previously, the bio was allocated before checking for a fatal signal.
If a signal was pending, the code would break out of the loop without
freeing or chaining the just-allocated bio, causing a memory leak.

This matches the pattern already used in __blkdev_issue_write_zeroes()
where the signal check precedes the allocation.

Fixes: bf86bcdb4012 ("blk-lib: check for kill signal in ioctl BLKZEROOUT")
Reported-by: syzbot+527a7e48a3d3d315d862@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=527a7e48a3d3d315d862
Signed-off-by: Shaurya Rane <ssrane_b23@...vjti.ac.in>
Reviewed-by: Keith Busch <kbusch@...nel.org>
---
 block/blk-lib.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/block/blk-lib.c b/block/blk-lib.c
index 3030a772d3aa..352e3c0f8a7d 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -202,13 +202,13 @@ static void __blkdev_issue_zero_pages(struct block_device *bdev,
 		unsigned int nr_vecs = __blkdev_sectors_to_bio_pages(nr_sects);
 		struct bio *bio;
 
-		bio = bio_alloc(bdev, nr_vecs, REQ_OP_WRITE, gfp_mask);
-		bio->bi_iter.bi_sector = sector;
-
 		if ((flags & BLKDEV_ZERO_KILLABLE) &&
 		    fatal_signal_pending(current))
 			break;
 
+		bio = bio_alloc(bdev, nr_vecs, REQ_OP_WRITE, gfp_mask);
+		bio->bi_iter.bi_sector = sector;
+
 		do {
 			unsigned int len;
 
-- 
2.34.1