linux-kernel - Forwarded: [PATCH] block: add allocation size check in blkdev_pr_read

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Message-ID: <693b69fa.a70a0220.33cd7b.0040.GAE@google.com>
Date: Thu, 11 Dec 2025 17:03:54 -0800
From: syzbot <syzbot+660d079d90f8a1baf54d@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Forwarded: [PATCH] block: add allocation size check in blkdev_pr_read_keys()

For archival purposes, forwarding an incoming command email to
linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com.

***

Subject: [PATCH] block: add allocation size check in blkdev_pr_read_keys()
Author: kartikey406@...il.com

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

blkdev_pr_read_keys() takes num_keys from userspace and uses it to
calculate the allocation size for keys_info via struct_size(). While
there is a check for SIZE_MAX (integer overflow), there is no upper
bound validation on the allocation size itself.

A malicious or buggy userspace can pass a large num_keys value that
doesn't trigger overflow but still results in an excessive allocation
attempt, causing a warning in the page allocator when the order exceeds
MAX_PAGE_ORDER.

Fix this by checking that keys_info_len does not exceed KMALLOC_MAX_SIZE
before attempting the allocation.

Reported-by: syzbot+660d079d90f8a1baf54d@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=660d079d90f8a1baf54d
Signed-off-by: Deepanshu Kartikey <kartikey406@...il.com>
---
 block/ioctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/ioctl.c b/block/ioctl.c
index 61feed686418..3e9e4257569f 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -443,7 +443,7 @@ static int blkdev_pr_read_keys(struct block_device *bdev, blk_mode_t mode,
 		return -EFAULT;

 	keys_info_len = struct_size(keys_info, keys, read_keys.num_keys);
-	if (keys_info_len == SIZE_MAX)
+	if (keys_info_len == SIZE_MAX || keys_info_len > KMALLOC_MAX_SIZE)
 		return -EINVAL;

 	keys_info = kzalloc(keys_info_len, GFP_KERNEL);
-- 
2.43.0