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futex: Sanitize cmpxchg_futex_value_locked API

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The cmpxchg_futex_value_locked API was funny in that it returned either
the original, user-exposed futex value OR an error code such as -EFAULT.
This was confusing at best, and could be a source of livelocks in places
that retry the cmpxchg_futex_value_locked after trying to fix the issue
by running fault_in_user_writeable().
    
This change makes the cmpxchg_futex_value_locked API more similar to the
get_futex_value_locked one, returning an error code and updating the
original value through a reference argument.
    
Signed-off-by: Michel Lespinasse <[email protected]>
Acked-by: Chris Metcalf <[email protected]>  [tile]
Acked-by: Tony Luck <[email protected]>  [ia64]
Acked-by: Thomas Gleixner <[email protected]>
Tested-by: Michal Simek <[email protected]>  [microblaze]
Acked-by: David Howells <[email protected]> [frv]
Cc: Darren Hart <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Matt Turner <[email protected]>
Cc: Russell King <[email protected]>
Cc: Ralf Baechle <[email protected]>
Cc: "James E.J. Bottomley" <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Cc: Paul Mundt <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Linus Torvalds <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
This commit is contained in:
Michel Lespinasse 2011-03-10 18:48:51 -08:00 • committed by Thomas Gleixner
commit 37a9d912b2
20 changed files with 144 additions and 132 deletions
Download patch file Download diff file Expand all files Collapse all files

18
arch/parisc/include/asm/futex.h
View file

@ -51,10 +51,10 @@ futex_atomic_op_inuser (int encoded_op, int __user *uaddr)
/* Non-atomic version */
static inline int
futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
futex_atomic_cmpxchg_inatomic(int *uval, int __user *uaddr,
int oldval, int newval)
{
int err = 0;
int uval;
int val;
/* futex.c wants to do a cmpxchg_inatomic on kernel NULL, which is
* our gateway page, and causes no end of trouble...
@ -65,12 +65,12 @@ futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
return -EFAULT;
err = get_user(uval, uaddr);
if (err) return -EFAULT;
if (uval == oldval)
err = put_user(newval, uaddr);
if (err) return -EFAULT;
return uval;
if (get_user(val, uaddr))
return -EFAULT;
if (val == oldval && put_user(newval, uaddr))
return -EFAULT;
*uval = val;
return 0;
}
#endif /*__KERNEL__*/