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Subject[PATCH] Fix compat_sys_sigpending breakage introduced by v4.13-rc1~6^2~12
The latest change of compat_sys_sigpending has broken it in two ways.

First, it tries to write 4 bytes more than userspace expects:
sizeof(old_sigset_t) == sizeof(long) == 8 instead of
sizeof(compat_old_sigset_t) == sizeof(u32) == 4.

Second, on big endian architectures these bytes are being written
in the wrong order.

This bug was found by strace test suite.

Reported-by: Anatoly Pugachev <matorola@gmail.com>
Inspired-by: Eugene Syromyatnikov <evgsyr@gmail.com>
Fixes: 8f13621abced ("sigpending(): move compat to native")
Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
---
kernel/signal.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index caed913..7e33f8c 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -3303,12 +3303,15 @@ SYSCALL_DEFINE1(sigpending, old_sigset_t __user *, set)
#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE1(sigpending, compat_old_sigset_t __user *, set32)
{
+#ifdef __BIG_ENDIAN
sigset_t set;
- int err = do_sigpending(&set, sizeof(old_sigset_t));
- if (err == 0)
- if (copy_to_user(set32, &set, sizeof(old_sigset_t)))
- err = -EFAULT;
+ int err = do_sigpending(&set, sizeof(set.sig[0]));
+ if (!err)
+ err = put_user(set.sig[0], set32);
return err;
+#else
+ return sys_rt_sigpending((sigset_t __user *)set32, sizeof(*set32));
+#endif
}
#endif

--
ldv
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