[PATCH] block: add allocation size check in blkdev_pr_read_keys()

[Deepanshu Kartikey <kartikey406@gmail.com>]

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.

Fixes: 22a1ffea5f80 ("block: add IOC_PR_READ_KEYS ioctl")
Reported-by: syzbot+660d079d90f8a1baf54d@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=660d079d90f8a1baf54d
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.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