Commit 98e626c1 authored Jan 24, 2023 by David Sterba Committed by Greg Kroah-Hartman Mar 03, 2023

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



[ Upstream commit 33e17b3f5ab74af12aca58c515bc8424ff69a343 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent ae03fa7a

fs/btrfs/send.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -7347,10 +7347,10 @@ long btrfs_ioctl_send(struct file mnt_file, 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;
		}