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 <jslaby@xxxxxxx> > Cc: Jeff Layton <jlayton@xxxxxxxxxxxxxxx> > Cc: "J. Bruce Fields" <bfields@xxxxxxxxxxxx> > Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx> > Cc: linux-fsdevel@xxxxxxxxxxxxxxx > --- > 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 <jlayton@xxxxxxxxxx>
