alpha: unbreak osf_setsysinfo(SSI_NVPAIRS, [SSIN_UACPROC, UAC_SIGBUS])
Sergei Trofimovich [Thu, 25 Aug 2011 22:59:02 +0000 (15:59 -0700)]
The bug was accidentally found by the following program:

    #include <asm/sysinfo.h>
    #include <asm/unistd.h>
    #include <sys/syscall.h>
    static int setsysinfo(unsigned long op, void *buffer, unsigned long size,
                          int *start, void *arg, unsigned long flag) {
        return syscall(__NR_osf_setsysinfo, op, buffer, size, start, arg, flag);
    }

    int main(int argc, char **argv) {
        short x[10];
        unsigned int buf[2] = { SSIN_UACPROC, UAC_SIGBUS, };
        setsysinfo(SSI_NVPAIRS, buf, 1, 0, 0, 0);

        int  *y = (int*) (x+1);
        *y = 0;
        return 0;
    }

The program shoud fail on SIGBUS, but didn't.

The patch is a second part of userspace flag fix (commit 745dd2405e28
"Alpha: Rearrange thread info flags fixing two regressions").

Deleted outdated out-of-sync 'UAC_SHIFT' (the cause of bug) in favour of
'ALPHA_UAC_SHIFT'.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
Acked-by: Michael Cree <mcree@orcon.net.nz>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/alpha/include/asm/sysinfo.h
arch/alpha/include/asm/thread_info.h
arch/alpha/kernel/osf_sys.c

index 086aba2..e77d77c 100644 (file)
 #define UAC_NOFIX                      2
 #define UAC_SIGBUS                     4
 
-
-#ifdef __KERNEL__
-
-/* This is the shift that is applied to the UAC bits as stored in the
-   per-thread flags.  See thread_info.h.  */
-#define UAC_SHIFT                      6
-
-#endif
-
 #endif /* __ASM_ALPHA_SYSINFO_H */
index 6f32f9c..ff73db0 100644 (file)
@@ -74,9 +74,9 @@ register struct thread_info *__current_thread_info __asm__("$8");
 #define TIF_NEED_RESCHED       3       /* rescheduling necessary */
 #define TIF_POLLING_NRFLAG     8       /* poll_idle is polling NEED_RESCHED */
 #define TIF_DIE_IF_KERNEL      9       /* dik recursion lock */
-#define TIF_UAC_NOPRINT                10      /* see sysinfo.h */
-#define TIF_UAC_NOFIX          11
-#define TIF_UAC_SIGBUS         12
+#define TIF_UAC_NOPRINT                10      /* ! Preserve sequence of following */
+#define TIF_UAC_NOFIX          11      /* ! flags as they match            */
+#define TIF_UAC_SIGBUS         12      /* ! userspace part of 'osf_sysinfo' */
 #define TIF_MEMDIE             13      /* is terminating due to OOM killer */
 #define TIF_RESTORE_SIGMASK    14      /* restore signal mask in do_signal */
 #define TIF_FREEZE             16      /* is freezing for suspend */
@@ -97,7 +97,7 @@ register struct thread_info *__current_thread_info __asm__("$8");
 #define _TIF_ALLWORK_MASK      (_TIF_WORK_MASK         \
                                 | _TIF_SYSCALL_TRACE)
 
-#define ALPHA_UAC_SHIFT                10
+#define ALPHA_UAC_SHIFT                TIF_UAC_NOPRINT
 #define ALPHA_UAC_MASK         (1 << TIF_UAC_NOPRINT | 1 << TIF_UAC_NOFIX | \
                                 1 << TIF_UAC_SIGBUS)
 
index 326f0a2..01e8715 100644 (file)
@@ -42,6 +42,7 @@
 #include <asm/uaccess.h>
 #include <asm/system.h>
 #include <asm/sysinfo.h>
+#include <asm/thread_info.h>
 #include <asm/hwrpb.h>
 #include <asm/processor.h>
 
@@ -633,9 +634,10 @@ SYSCALL_DEFINE5(osf_getsysinfo, unsigned long, op, void __user *, buffer,
        case GSI_UACPROC:
                if (nbytes < sizeof(unsigned int))
                        return -EINVAL;
-               w = (current_thread_info()->flags >> UAC_SHIFT) & UAC_BITMASK;
-               if (put_user(w, (unsigned int __user *)buffer))
-                       return -EFAULT;
+               w = (current_thread_info()->flags >> ALPHA_UAC_SHIFT) &
+                       UAC_BITMASK;
+               if (put_user(w, (unsigned int __user *)buffer))
+                       return -EFAULT;
                return 1;
 
        case GSI_PROC_TYPE:
@@ -756,8 +758,8 @@ SYSCALL_DEFINE5(osf_setsysinfo, unsigned long, op, void __user *, buffer,
                        case SSIN_UACPROC:
                        again:
                                old = current_thread_info()->flags;
-                               new = old & ~(UAC_BITMASK << UAC_SHIFT);
-                               new = new | (w & UAC_BITMASK) << UAC_SHIFT;
+                               new = old & ~(UAC_BITMASK << ALPHA_UAC_SHIFT);
+                               new = new | (w & UAC_BITMASK) << ALPHA_UAC_SHIFT;
                                if (cmpxchg(&current_thread_info()->flags,
                                            old, new) != old)
                                        goto again;