commit 2df7a7d1cd07626dd235ca102830ebfc6c01a09e
author Sergei Trofimovich <slyfox@gentoo.org> Thu Aug 25 15:59:02 2011 -0700
committer Linus Torvalds <torvalds@linux-foundation.org> Thu Aug 25 16:25:33 2011 -0700
tree db226e5a1728f600e8f711400e97098023f3c2f4
parent 06ed4625fdfffee1251708cd30de276186d5fdcf

alpha: unbreak osf_setsysinfo(SSI_NVPAIRS, [SSIN_UACPROC, UAC_SIGBUS])

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Deleted outdated out-of-sync 'UAC_SHIFT' (the cause of bug) in favour of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/kernel/osf_sys.c

diff --git a/arch/alpha/kernel/osf_sys.c b/arch/alpha/kernel/osf_sys.c
index 326f0a2..01e8715 100644
--- a/arch/alpha/kernel/osf_sys.c
+++ b/arch/alpha/kernel/osf_sys.c
@@ -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 @@
  	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 @@
  			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;