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

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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    6bda50f4333f Merge tag 'mips-fixes_6.18_2' of git://git.ke..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17ad8192580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f30cc590c4f6da44
dashboard link: https://syzkaller.appspot.com/bug?extid=527a7e48a3d3d315d862
compiler:       gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10b27cb4580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/864951cecf67/disk-6bda50f4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4692a21b76e7/vmlinux-6bda50f4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a2898beb8301/bzImage-6bda50f4.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/384c8ab49dd6/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+527a7e48a3d3d315d862@syzkaller.appspotmail.com

BUG: memory leak
unreferenced object 0xffff88810dd11b00 (size 200):
  comm "syz.3.32", pid 6189, jiffies 4294946488
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 80 70 01 41 81 88 ff ff  .........p.A....
    01 00 00 00 00 00 00 00 00 00 00 00 01 00 00 00  ................
  backtrace (crc fe2a8999):
    kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
    slab_post_alloc_hook mm/slub.c:4983 [inline]
    slab_alloc_node mm/slub.c:5288 [inline]
    kmem_cache_alloc_noprof+0x397/0x5a0 mm/slub.c:5295
    mempool_alloc_noprof+0xa0/0x200 mm/mempool.c:426
    bio_alloc_bioset+0x398/0x7b0 block/bio.c:558
    bio_alloc include/linux/bio.h:372 [inline]
    __blkdev_issue_zero_pages+0x109/0x2f0 block/blk-lib.c:205
    blkdev_issue_zero_pages block/blk-lib.c:239 [inline]
    blkdev_issue_zeroout+0x1dc/0x490 block/blk-lib.c:326
    blk_ioctl_zeroout block/ioctl.c:250 [inline]
    blkdev_common_ioctl+0xb40/0x1180 block/ioctl.c:580
    blkdev_ioctl+0x128/0x380 block/ioctl.c:699
    vfs_ioctl fs/ioctl.c:51 [inline]
    __do_sys_ioctl fs/ioctl.c:597 [inline]
    __se_sys_ioctl fs/ioctl.c:583 [inline]
    __x64_sys_ioctl+0xf4/0x140 fs/ioctl.c:583
    do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
    do_syscall_64+0xa4/0xfa0 arch/x86/entry/syscall_64.c:94
    entry_SYSCALL_64_after_hwframe+0x77/0x7f

BUG: memory leak
unreferenced object 0xffff888108a3d000 (size 4096):
  comm "syz.3.32", pid 6189, jiffies 4294946488
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace (crc 0):
    kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
    slab_post_alloc_hook mm/slub.c:4983 [inline]
    slab_alloc_node mm/slub.c:5288 [inline]
    kmem_cache_alloc_noprof+0x397/0x5a0 mm/slub.c:5295
    mempool_alloc_noprof+0xa0/0x200 mm/mempool.c:426
    bvec_alloc+0x9d/0x130 block/bio.c:210
    bio_alloc_bioset+0x3cb/0x7b0 block/bio.c:573
    bio_alloc include/linux/bio.h:372 [inline]
    __blkdev_issue_zero_pages+0x109/0x2f0 block/blk-lib.c:205
    blkdev_issue_zero_pages block/blk-lib.c:239 [inline]
    blkdev_issue_zeroout+0x1dc/0x490 block/blk-lib.c:326
    blk_ioctl_zeroout block/ioctl.c:250 [inline]
    blkdev_common_ioctl+0xb40/0x1180 block/ioctl.c:580
    blkdev_ioctl+0x128/0x380 block/ioctl.c:699
    vfs_ioctl fs/ioctl.c:51 [inline]
    __do_sys_ioctl fs/ioctl.c:597 [inline]
    __se_sys_ioctl fs/ioctl.c:583 [inline]
    __x64_sys_ioctl+0xf4/0x140 fs/ioctl.c:583
    do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
    do_syscall_64+0xa4/0xfa0 arch/x86/entry/syscall_64.c:94
    entry_SYSCALL_64_after_hwframe+0x77/0x7f

connection error: failed to recv *flatrpc.ExecutorMessageRawT: EOF


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

[shaurya]

[-- Attachment #1: Type: text/plain, Size: 84 bytes --]

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


[-- Attachment #2: 0001-block-fix-memory-leak-in-__blkdev_issue_zero_pages.patch --]
[-- Type: text/x-patch, Size: 1463 bytes --]

From 79fe005d08f4f81f422a371fd7d4d3cd2580a65f Mon Sep 17 00:00:00 2001
From: Shaurya Rane <ssrane_b23@ee.vjti.ac.in>
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@ee.vjti.ac.in>
---
 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

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

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+527a7e48a3d3d315d862@syzkaller.appspotmail.com
Tested-by: syzbot+527a7e48a3d3d315d862@syzkaller.appspotmail.com

Tested on:

commit:         559e608c Merge tag 'ntfs3_for_6.19' of https://github...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1787eab4580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=3bdbe6509b080086
dashboard link: https://syzkaller.appspot.com/bug?extid=527a7e48a3d3d315d862
compiler:       gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=11f2301a580000

Note: testing is done by a robot and is best-effort only.

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

[Keith Busch]

On Thu, Dec 04, 2025 at 09:42:38PM +0530, shaurya wrote:
> 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@ee.vjti.ac.in>

Looks good.

Reviewed-by: Keith Busch <kbusch@kernel.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;
>  
> -- 

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

[Hannes Reinecke]

On 12/4/25 17:12, shaurya wrote:
> #syz test:
> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
 >

Please send the patch as the mail body, not as attachment.
Otherwise bots will have issues picking it up properly.
Other than that:

Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich