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SubjectRe: [PATCH][COMPAT] compat_sys_fcntl{,64} 1/9 Generic part
Hi Andi,

Thanks for the comments.

From: Andi Kleen <ak@muc.de>
>
> On Fri, Feb 28, 2003 at 05:33:49AM +0100, Stephen Rothwell wrote:
> > +static int get_compat_flock(struct flock *kfl, struct compat_flock *ufl)
> > +{
> > + if (!access_ok(VERIFY_READ, ufl, sizeof(*ufl)) ||
> > + __get_user(kfl->l_type, &ufl->l_type) ||
> > + __get_user(kfl->l_whence, &ufl->l_whence) ||
> > + __get_user(kfl->l_start, &ufl->l_start) ||
> > + __get_user(kfl->l_len, &ufl->l_len) ||
> > + __get_user(kfl->l_pid, &ufl->l_pid))
>
> Perhaps there should be really a big fat comment on top of compat.c
> that it depends on a hole on __PAGE_OFFSET if the arch allows passing
> 64bit pointers to the compat functions.

One of my tasks is to document all the assumptions in hte comapt code
(and there a a few - and I find more as I go :-)). However, could you
elaborate a bit here - do you mean passing 64 bit pointers from user mode?

> > +asmlinkage long compat_sys_fcntl(unsigned int fd, unsigned int cmd,
> > + unsigned long arg)
> > +{
> > + if ((cmd == F_GETLK64) || (cmd == F_SETLK64) || (cmd == F_SETLKW64))
> > + return -EINVAL;
>
> That won't work for IA32 emulation. There are programs that call
> old style fcntl() with F_*LK64. Just drop the if here.

I was going to elaborate on this when I sent the x86_64 part of the patch.
If you read the "normal" kernel fcntl function, it does NOT accept
F_GETLK64, F_SETLK64 or F_SETLKW64 through the fcntl sys call only
through the fcntl64 syscall. So any program that does call the old
style fcntl() with one of those will fail on ia32 - which is what you are
trying to emulate.

Cheers,
Stephen
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