On 13/08/11 09:01, Sergei Trofimovich wrote:

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:

quoted

commit 745dd2405e281d96c0a449103bdf6a895048f28c
Author: Michael Cree [off-list ref]
Date:   Mon Nov 30 22:44:40 2009 -0500

   Alpha: Rearrange thread info flags fixing two regressions

   Both regressions fixed by (1) rearranging TIF_NOTIFY_RESUME flag to be
   in lower 8 bits of the thread info flags, and (2) making sure that
   ALPHA_UAC_SHIFT matches the rearrangement of the thread info flags.

Deleted outdated out-of-sync 'UAC_SHIFT' (the cause of bug) in favour of 'ALPHA_UAC_SHIFT'.

Signed-off-by: Sergei Trofimovich <redacted>
Cc: linux-alpha@vger.kernel.org
Cc: Michael Cree <redacted>
Cc: Richard Henderson <redacted>
Cc: Ivan Kokshaysky <redacted>
Cc: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/include/asm/sysinfo.h     |    9 ---------
 arch/alpha/include/asm/thread_info.h |    8 ++++----
 arch/alpha/kernel/osf_sys.c          |    7 ++++---
 3 files changed, 8 insertions(+), 16 deletions(-)

Looks good to me.

Acked-by: Michael Cree <redacted>

Thanks
Michael.