1 files changed, 18 insertions, 4 deletions

diff --git a/fs/compat.c b/fs/compat.c
index 55ac0324aaf1..271b75d1597f 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -494,9 +494,21 @@ asmlinkage long compat_sys_fcntl64(unsigned int fd, unsigned int cmd,
                 ret = sys_fcntl(fd, cmd, (unsigned long)&f);
                 set_fs(old_fs);
                 if (cmd == F_GETLK && ret == 0) {
-                        if ((f.l_start >= COMPAT_OFF_T_MAX) ||
-                            ((f.l_start + f.l_len) > COMPAT_OFF_T_MAX))
+                        /* GETLK was successfule and we need to return the data...
+                         * but it needs to fit in the compat structure.
+                         * l_start shouldn't be too big, unless the original
+                         * start + end is greater than COMPAT_OFF_T_MAX, in which
+                         * case the app was asking for trouble, so we return
+                         * -EOVERFLOW in that case.
+                         * l_len could be too big, in which case we just truncate it,
+                         * and only allow the app to see that part of the conflicting
+                         * lock that might make sense to it anyway
+                         */
+
+                        if (f.l_start > COMPAT_OFF_T_MAX)
                                 ret = -EOVERFLOW;
+                        if (f.l_len > COMPAT_OFF_T_MAX)
+                                f.l_len = COMPAT_OFF_T_MAX;
                         if (ret == 0)
                                 ret = put_compat_flock(&f, compat_ptr(arg));
                 }
@@ -515,9 +527,11 @@ asmlinkage long compat_sys_fcntl64(unsigned int fd, unsigned int cmd,
                                 (unsigned long)&f);
                 set_fs(old_fs);
                 if (cmd == F_GETLK64 && ret == 0) {
-                        if ((f.l_start >= COMPAT_LOFF_T_MAX) ||
-                            ((f.l_start + f.l_len) > COMPAT_LOFF_T_MAX))
+                        /* need to return lock information - see above for commentary */
+                        if (f.l_start > COMPAT_LOFF_T_MAX)
                                 ret = -EOVERFLOW;
+                        if (f.l_len > COMPAT_LOFF_T_MAX)
+                                f.l_len = COMPAT_LOFF_T_MAX;
                         if (ret == 0)
                                 ret = put_compat_flock64(&f, compat_ptr(arg));
                 }