Commit a58383fa authored by Deepanshu Kartikey's avatar Deepanshu Kartikey Committed by Jens Axboe
Browse files

block: add allocation size check in blkdev_pr_read_keys() 



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 introducing PR_KEYS_MAX to limit the number of keys to
a sane value. This makes the SIZE_MAX check redundant, so remove it.
Also switch to kvzalloc/kvfree to handle larger allocations gracefully.

Fixes: 22a1ffea ("block: add IOC_PR_READ_KEYS ioctl")
Tested-by: default avatar <syzbot+660d079d90f8a1baf54d@syzkaller.appspotmail.com>
Reported-by: default avatar <syzbot+660d079d90f8a1baf54d@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=660d079d90f8a1baf54d
Link: https://lore.kernel.org/all/20251212013510.3576091-1-kartikey406@gmail.com/T/

 [v1]
Signed-off-by: default avatarDeepanshu Kartikey <kartikey406@gmail.com>
Reviewed-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 67d85b06

block/ioctl.c

+5 −4
Original line number Diff line number Diff line
@@ -442,11 +442,12 @@ static int blkdev_pr_read_keys(struct block_device *bdev, blk_mode_t mode, 
	if (copy_from_user(&read_keys, arg, sizeof(read_keys)))

		return -EFAULT;



	keys_info_len = struct_size(keys_info, keys, read_keys.num_keys);

	if (keys_info_len == SIZE_MAX)

	if (read_keys.num_keys > PR_KEYS_MAX)

		return -EINVAL;



	keys_info = kzalloc(keys_info_len, GFP_KERNEL);

	keys_info_len = struct_size(keys_info, keys, read_keys.num_keys);



	keys_info = kvzalloc(keys_info_len, GFP_KERNEL);

	if (!keys_info)

		return -ENOMEM;
@@ -473,7 +474,7 @@ static int blkdev_pr_read_keys(struct block_device *bdev, blk_mode_t mode, 
	if (copy_to_user(arg, &read_keys, sizeof(read_keys)))

		ret = -EFAULT;

out:

	kfree(keys_info);

	kvfree(keys_info);

	return ret;

}

include/uapi/linux/pr.h

+2 −0
Original line number Diff line number Diff line
@@ -79,4 +79,6 @@ struct pr_read_reservation { 
#define IOC_PR_READ_KEYS	_IOWR('p', 206, struct pr_read_keys)

#define IOC_PR_READ_RESERVATION	_IOR('p', 207, struct pr_read_reservation)



#define PR_KEYS_MAX		(1u << 16)



#endif /* _UAPI_PR_H */