On Wed, Dec 17, 2025 at 07:17:12AM +0530, Deepanshu Kartikey wrote: > 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: 22a1ffea5f80 ("block: add IOC_PR_READ_KEYS ioctl") > Tested-by: syzbot+660d079d90f8a1baf54d@syzkaller.appspotmail.com > Reported-by: 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: Deepanshu Kartikey > --- > v3: > - Renamed PR_KEYS_MAX_NUM to PR_KEYS_MAX > - Moved define to include/uapi/linux/pr.h > v2: > - Added PR_KEYS_MAX_NUM (64K) limit instead of checking KMALLOC_MAX_SIZE > - Removed redundant SIZE_MAX check > - Switched to kvzalloc/kvfree > --- > block/ioctl.c | 9 +++++---- > include/uapi/linux/pr.h | 2 ++ > 2 files changed, 7 insertions(+), 4 deletions(-) Reviewed-by: Stefan Hajnoczi