[PATCH] sys_pselect7 vs compat_sys_pselect7 uaccess error handling

758333458aa719bfc26ec16eafd4ad3a9e96014d fixes the not checked copy_to_user
return value of compat_sys_pselect7.  I ran into this too because of an old
source tree, but my fix would look quite a bit different to Andi's fix.

The reason is that the compat function IMHO should behave the very same as
the non-compat function if possible.  Since sys_pselect7 does not return
-EFAULT in this specific case, change the compat code so it behaves like
sys_pselect7.

Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 17 insertions, 3 deletions

diff --git a/fs/compat.c b/fs/compat.c
index 50624d4a70c6..8d0a0018a7d2 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -1835,9 +1835,12 @@ asmlinkage long compat_sys_pselect7(int n, compat_ulong_t __user *inp,
 
         } while (!ret && !timeout && tsp && (ts.tv_sec || ts.tv_nsec));
 
-        if (ret == 0 && tsp && !(current->personality & STICKY_TIMEOUTS)) {
+        if (tsp) {
                 struct compat_timespec rts;
 
+                if (current->personality & STICKY_TIMEOUTS)
+                        goto sticky;
+
                 rts.tv_sec = timeout / HZ;
                 rts.tv_nsec = (timeout % HZ) * (NSEC_PER_SEC/HZ);
                 if (rts.tv_nsec >= NSEC_PER_SEC) {
@@ -1846,8 +1849,19 @@ asmlinkage long compat_sys_pselect7(int n, compat_ulong_t __user *inp,
                 }
                 if (compat_timespec_compare(&rts, &ts) >= 0)
                         rts = ts;
-                if (copy_to_user(tsp, &rts, sizeof(rts)))
-                        ret = -EFAULT;
+                if (copy_to_user(tsp, &rts, sizeof(rts))) {
+sticky:
+                        /*
+                         * If an application puts its timeval in read-only
+                         * memory, we don't want the Linux-specific update to
+                         * the timeval to cause a fault after the select has
+                         * completed successfully. However, because we're not
+                         * updating the timeval, we can't restart the system
+                         * call.
+                         */
+                        if (ret == -ERESTARTNOHAND)
+                                ret = -EINTR;
+                }
         }
 
         if (ret == -ERESTARTNOHAND) {