This is a note to let you know that I've just added the patch titled btrfs: send: limit number of clones and allocated memory size to the 4.19-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: btrfs-send-limit-number-of-clones-and-allocated-memo.patch and it can be found in the queue-4.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 91b51e5f59c9a956b1f36d07481ca381f19cdf0c Author: David Sterba <dsterba@xxxxxxxx> Date: Tue Jan 24 20:32:10 2023 +0100 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@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: David Sterba <dsterba@xxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c index 80d248e88761d..1f535cd990d3c 100644 --- a/fs/btrfs/send.c +++ b/fs/btrfs/send.c @@ -6826,10 +6826,10 @@ 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; }