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    Subject[PATCH 116/241] sparc64: not any error from do_sigaltstack() should fail rt_sigreturn()
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    3.5.7.2 -stable review patch.  If anyone has any objections, please let me know.

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

    From: Al Viro <viro@zeniv.linux.org.uk>

    commit fae2ae2a900a5c7bb385fe4075f343e7e2d5daa2 upstream.

    If a signal handler is executed on altstack and another signal comes,
    we will end up with rt_sigreturn() on return from the second handler
    getting -EPERM from do_sigaltstack(). It's perfectly OK, since we
    are not asking to change the settings; in fact, they couldn't have been
    changed during the second handler execution exactly because we'd been
    on altstack all along. 64bit sigreturn on sparc treats any error from
    do_sigaltstack() as "SIGSEGV now"; we need to switch to the same semantics
    we are using on other architectures.

    Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
    ---
    arch/sparc/kernel/signal_64.c | 4 +---
    1 file changed, 1 insertion(+), 3 deletions(-)

    diff --git a/arch/sparc/kernel/signal_64.c b/arch/sparc/kernel/signal_64.c
    index 867de2f..689e1ba 100644
    --- a/arch/sparc/kernel/signal_64.c
    +++ b/arch/sparc/kernel/signal_64.c
    @@ -295,9 +295,7 @@ void do_rt_sigreturn(struct pt_regs *regs)
    err |= restore_fpu_state(regs, fpu_save);

    err |= __copy_from_user(&set, &sf->mask, sizeof(sigset_t));
    - err |= do_sigaltstack(&sf->stack, NULL, (unsigned long)sf);
    -
    - if (err)
    + if (err || do_sigaltstack(&sf->stack, NULL, (unsigned long)sf) == -EFAULT)
    goto segv;

    err |= __get_user(rwin_save, &sf->rwin_save);
    --
    1.7.9.5


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