Re: [syzbot] [block?] [udf?] memory leak in __blkdev_issue_zero_pages

[shaurya]

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

From 79fe005d08f4f81f422a371fd7d4d3cd2580a65f Mon Sep 17 00:00:00 2001
From: Shaurya Rane <ssrane_b23@xxxxxxxxxxxxx>
Date: Thu, 4 Dec 2025 21:38:51 +0530
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.

Signed-off-by: Shaurya Rane <ssrane_b23@xxxxxxxxxxxxx>
---
 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