This is a note to let you know that we have just queued up the patch titled
Subject: PARISC futex: special case cmpxchg NULL in kernel space
to the 2.6.24-stable tree. Its filename is
parisc-futex-special-case-cmpxchg-null-in-kernel-space.patch
A git repo of this tree can be found at
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
>From stable-bounces@xxxxxxxxxxxxxxxx Wed Apr 16 16:44:42 2008
From: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
To: stable@xxxxxxxxxx
Date: Tue, 15 Apr 2008 10:45:11 -0500
Message-Id: <1208274312.3131.11.camel@xxxxxxxxxxxxxxxxxxxxx>
Cc: Parisc List <linux-parisc@xxxxxxxxxxxxxxx>
Subject: PARISC futex: special case cmpxchg NULL in kernel space
From: Kyle McMartin <kyle@xxxxxxxxxxxxxxxxx>
upstream commit: c20a84c91048c76c1379011c96b1a5cee5c7d9a0
commit f9e77acd4060fefbb60a351cdb8d30fca27fe194
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Date: Sun Feb 24 02:10:05 2008 +0000
futex: runtime enable pi and robust functionality
which was backported to stable based on mainline Commit
a0c1e9073ef7428a14309cba010633a6cd6719ea added code to futex.c
to detect whether futex_atomic_cmpxchg_inatomic was implemented at run
time:
+ curval = cmpxchg_futex_value_locked(NULL, 0, 0);
+ if (curval == -EFAULT)
+ futex_cmpxchg_enabled = 1;
This is bogus on parisc, since page zero in kernel virtual space is the
gateway page for syscall entry, and should not be read from the kernel.
(That, and we really don't like the kernel faulting on its own address
space...)
Signed-off-by: Kyle McMartin <kyle@xxxxxxxxxxx>
Signed-off-by: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Chris Wright <chrisw@xxxxxxxxxxxx>
---
include/asm-parisc/futex.h | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
--- a/include/asm-parisc/futex.h
+++ b/include/asm-parisc/futex.h
@@ -56,6 +56,12 @@ futex_atomic_cmpxchg_inatomic(int __user
int err = 0;
int uval;
+ /* futex.c wants to do a cmpxchg_inatomic on kernel NULL, which is
+ * our gateway page, and causes no end of trouble...
+ */
+ if (segment_eq(KERNEL_DS, get_fs()) && !uaddr)
+ return -EFAULT;
+
if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
return -EFAULT;
@@ -67,5 +73,5 @@ futex_atomic_cmpxchg_inatomic(int __user
return uval;
}
-#endif
-#endif
+#endif /*__KERNEL__*/
+#endif /*_ASM_PARISC_FUTEX_H*/
Patches currently in stable-queue which might be from James.Bottomley@xxxxxxxxxxxxxxxxxxxxx are
queue-2.6.24/parisc-pdc_console-fix-bizarre-panic-on-boot.patch
queue-2.6.24/parisc-futex-special-case-cmpxchg-null-in-kernel-space.patch
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