On Tue, 2017-06-13 at 11:22 +0200, Jiri Slaby wrote:
> fcntl(0, F_SETOWN, 0x80000000) triggers:
> UBSAN: Undefined behaviour in fs/fcntl.c:118:7
> negation of -2147483648 cannot be represented in type 'int':
> CPU: 1 PID: 18261 Comm: syz-executor Not tainted 4.8.1-0-syzkaller #1
> ...
> Call Trace:
> ...
> [<ffffffffad8f0868>] ? f_setown+0x1d8/0x200
> [<ffffffffad8f19a9>] ? SyS_fcntl+0x999/0xf30
> [<ffffffffaed1fb00>] ? entry_SYSCALL_64_fastpath+0x23/0xc1
>
> Fix that by checking the arg parameter properly (against INT_MAX) before
> "who = -who". And return immediatelly with -EINVAL in case it is wrong.
> Note that according to POSIX we can return EINVAL:
> http://pubs.opengroup.org/onlinepubs/9699919799/functions/fcntl.html
>
> [EINVAL]
> The cmd argument is F_SETOWN and the value of the argument
> is not valid as a process or process group identifier.
>
> [v2] returns an error, v1 used to fail silently
>
> Signed-off-by: Jiri Slaby <jsl...@suse.cz>
> Cc: Jeff Layton <jlay...@poochiereds.net>
> Cc: "J. Bruce Fields" <bfie...@fieldses.org>
> Cc: Alexander Viro <v...@zeniv.linux.org.uk>
> Cc: linux-fsde...@vger.kernel.org
> ---
> fs/fcntl.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/fs/fcntl.c b/fs/fcntl.c
> index 313eba860346..db853670e22f 100644
> --- a/fs/fcntl.c
> +++ b/fs/fcntl.c
> @@ -114,6 +114,10 @@ int f_setown(struct file *filp, unsigned long arg, int
> force)
> enum pid_type type;
> struct pid *pid;
> int who = arg;
> +
> + if (arg > INT_MAX)
> + return -EINVAL;
> +
> type = PIDTYPE_PID;
> if (who < 0) {
> type = PIDTYPE_PGID;
The next part here says:
if (who < 0) {
type = PIDTYPE_PGID;
who = -who;
}
Won't this break the ability to pass in a pgid? Valid negative values
will end up getting back -EINVAL here, AFAICT.
--
Jeff Layton <jlay...@redhat.com>
