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    Subject[PATCH 3.2 079/107] s390/compat: correct uc_sigmask of the compat signal frame
    3.2.72-rc1 review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Martin Schwidefsky <schwidefsky@de.ibm.com>

    commit 8d4bd0ed0439dfc780aab801a085961925ed6838 upstream.

    The uc_sigmask in the ucontext structure is an array of words to keep
    the 64 signal bits (or 1024 if you ask glibc but the kernel sigset_t
    only has 64 bits).

    For 64 bit the sigset_t contains a single 8 byte word, but for 31 bit
    there are two 4 byte words. The compat signal handler code uses a
    simple copy of the 64 bit sigset_t to the 31 bit compat_sigset_t.
    As s390 is a big-endian architecture this is incorrect, the two words
    in the 31 bit sigset_t array need to be swapped.

    Reported-by: Stefan Liebler <stli@linux.vnet.ibm.com>
    Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
    [bwh: Backported to 3.2:
    - Introduce local compat_sigset_t in setup_frame32()
    - Adjust context]
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    arch/s390/kernel/compat_signal.c | 27 +++++++++++++++++++++++----
    1 file changed, 23 insertions(+), 4 deletions(-)

    --- a/arch/s390/kernel/compat_signal.c
    +++ b/arch/s390/kernel/compat_signal.c
    @@ -52,6 +52,19 @@ typedef struct
    __u32 gprs_high[NUM_GPRS];
    } rt_sigframe32;

    +static inline void sigset_to_sigset32(unsigned long *set64,
    + compat_sigset_word *set32)
    +{
    + set32[0] = (compat_sigset_word) set64[0];
    + set32[1] = (compat_sigset_word)(set64[0] >> 32);
    +}
    +
    +static inline void sigset32_to_sigset(compat_sigset_word *set32,
    + unsigned long *set64)
    +{
    + set64[0] = (unsigned long) set32[0] | ((unsigned long) set32[1] << 32);
    +}
    +
    int copy_siginfo_to_user32(compat_siginfo_t __user *to, siginfo_t *from)
    {
    int err;
    @@ -361,12 +374,14 @@ asmlinkage long sys32_sigreturn(void)
    {
    struct pt_regs *regs = task_pt_regs(current);
    sigframe32 __user *frame = (sigframe32 __user *)regs->gprs[15];
    + compat_sigset_t cset;
    sigset_t set;

    if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
    goto badframe;
    - if (__copy_from_user(&set.sig, &frame->sc.oldmask, _SIGMASK_COPY_SIZE32))
    + if (__copy_from_user(&cset.sig, &frame->sc.oldmask, _SIGMASK_COPY_SIZE32))
    goto badframe;
    + sigset32_to_sigset(cset.sig, set.sig);
    sigdelsetmask(&set, ~_BLOCKABLE);
    set_current_blocked(&set);
    if (restore_sigregs32(regs, &frame->sregs))
    @@ -383,6 +398,7 @@ asmlinkage long sys32_rt_sigreturn(void)
    {
    struct pt_regs *regs = task_pt_regs(current);
    rt_sigframe32 __user *frame = (rt_sigframe32 __user *)regs->gprs[15];
    + compat_sigset_t cset;
    sigset_t set;
    stack_t st;
    __u32 ss_sp;
    @@ -391,8 +407,9 @@ asmlinkage long sys32_rt_sigreturn(void)

    if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
    goto badframe;
    - if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
    + if (__copy_from_user(&cset, &frame->uc.uc_sigmask, sizeof(cset)))
    goto badframe;
    + sigset32_to_sigset(cset.sig, set.sig);
    sigdelsetmask(&set, ~_BLOCKABLE);
    set_current_blocked(&set);
    if (restore_sigregs32(regs, &frame->uc.uc_mcontext))
    @@ -464,13 +481,16 @@ static int setup_frame32(int sig, struct
    sigset_t *set, struct pt_regs * regs)
    {
    sigframe32 __user *frame = get_sigframe(ka, regs, sizeof(sigframe32));
    + compat_sigset_t cset;
    +
    if (!access_ok(VERIFY_WRITE, frame, sizeof(sigframe32)))
    goto give_sigsegv;

    if (frame == (void __user *) -1UL)
    goto give_sigsegv;

    - if (__copy_to_user(&frame->sc.oldmask, &set->sig, _SIGMASK_COPY_SIZE32))
    + sigset_to_sigset32(set->sig, cset.sig);
    + if (__copy_to_user(&frame->sc.oldmask, &cset.sig, _SIGMASK_COPY_SIZE32))
    goto give_sigsegv;

    if (save_sigregs32(regs, &frame->sregs))
    @@ -524,6 +544,7 @@ give_sigsegv:
    static int setup_rt_frame32(int sig, struct k_sigaction *ka, siginfo_t *info,
    sigset_t *set, struct pt_regs * regs)
    {
    + compat_sigset_t cset;
    int err = 0;
    rt_sigframe32 __user *frame = get_sigframe(ka, regs, sizeof(rt_sigframe32));
    if (!access_ok(VERIFY_WRITE, frame, sizeof(rt_sigframe32)))
    @@ -536,6 +557,7 @@ static int setup_rt_frame32(int sig, str
    goto give_sigsegv;

    /* Create the ucontext. */
    + sigset_to_sigset32(set->sig, cset.sig);
    err |= __put_user(UC_EXTENDED, &frame->uc.uc_flags);
    err |= __put_user(0, &frame->uc.uc_link);
    err |= __put_user(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
    @@ -544,7 +566,7 @@ static int setup_rt_frame32(int sig, str
    err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
    err |= save_sigregs32(regs, &frame->uc.uc_mcontext);
    err |= save_sigregs_gprs_high(regs, frame->gprs_high);
    - err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
    + err |= __copy_to_user(&frame->uc.uc_sigmask, &cset, sizeof(cset));
    if (err)
    goto give_sigsegv;



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