Commit 33e17b3f authored Jan 24, 2023 by David Sterba

btrfs: send: limit number of clones and allocated memory size

The arg->clone_sources_count is u64 and can trigger a warning when a
huge value is passed from user space and a huge array is allocated.
Limit the allocated memory to 8MiB (can be increased if needed), which
in turn limits the number of clone sources to 8M / sizeof(struct
clone_root) = 8M / 40 = 209715. Real world number of clones is from
tens to hundreds, so this is future proof.

Reported-by: <syzbot+4376a9a073770c173269@syzkaller.appspotmail.com>
Signed-off-by: David Sterba <dsterba@suse.com>

parent eadd7dec

fs/btrfs/send.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -8072,10 +8072,10 @@ long btrfs_ioctl_send(struct inode inode, struct btrfs_ioctl_send_args arg)
		/*
		* Check that we don't overflow at later allocations, we request
		* clone_sources_count + 1 items, and compare to unsigned long inside
		* access_ok.
		* access_ok. Also set an upper limit for allocation size so this can't
		* easily exhaust memory. Max number of clone sources is about 200K.
		*/
		if (arg->clone_sources_count >
		ULONG_MAX / sizeof(struct clone_root) - 1) {
		if (arg->clone_sources_count > SZ_8M / sizeof(struct clone_root)) {
		ret = -EINVAL;
		goto out;
		}