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    Subject[PATCH AUTOSEL 6.1 11/24] btrfs: send: limit number of clones and allocated memory size
    Date
    From: David Sterba <dsterba@suse.com>

    [ 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>
    ---
    fs/btrfs/send.c | 6 +++---
    1 file changed, 3 insertions(+), 3 deletions(-)

    diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
    index 1c4b693ee4a3a..937b60ae576e0 100644
    --- a/fs/btrfs/send.c
    +++ b/fs/btrfs/send.c
    @@ -7839,10 +7839,10 @@ 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;
    }
    --
    2.39.0
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