commit ebce1719ac0a2a71b64742ecf1c9ec2497a65a55
author Patrick Venture <venture@google.com> Wed Jan 26 13:25:59 2022 -0800
committer Laurent Vivier <laurent@vivier.eu> Thu Jan 27 16:58:33 2022 +0100
tree df9607ba59dab089d241824ed7cb44f6599f0b22
parent d3ced2a59a543b3c3fc7dee2e64ee360e9a698cd

linux-user: sigprocmask check read perms first

Linux kernel now checks the read permissions before validating `how`

Suggested-by: Laurent Vivier <laurent@vivier.eu>
Signed-off-by: Patrick Venture <venture@google.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20220126212559.1936290-3-venture@google.com>
[lv: remove unneeded ")"]
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

linux-user/syscall.c

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 9f8b497..84cfa22 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -9435,6 +9435,13 @@
             int how;
 
             if (arg2) {
+                p = lock_user(VERIFY_READ, arg2, sizeof(target_sigset_t), 1);
+                if (!p) {
+                    return -TARGET_EFAULT;
+                }
+                target_to_host_old_sigset(&set, p);
+                unlock_user(p, arg2, 0);
+                set_ptr = &set;
                 switch (arg1) {
                 case TARGET_SIG_BLOCK:
                     how = SIG_BLOCK;
@@ -9448,11 +9455,6 @@
                 default:
                     return -TARGET_EINVAL;
                 }
-                if (!(p = lock_user(VERIFY_READ, arg2, sizeof(target_sigset_t), 1)))
-                    return -TARGET_EFAULT;
-                target_to_host_old_sigset(&set, p);
-                unlock_user(p, arg2, 0);
-                set_ptr = &set;
             } else {
                 how = 0;
                 set_ptr = NULL;