Re: [PATCH v2 2/2] linux-user: sigprocmask check read perms first

[Laurent Vivier]

Le 26/01/2022 à 18:58, Patrick Venture a écrit :

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

Suggested-by: Laurent Vivier <laur...@vivier.eu>
Signed-off-by: Patrick Venture <vent...@google.com>

Reviewed-by: Laurent Vivier <laur...@vivier.eu>

---
  linux-user/syscall.c | 12 +++++++-----
  1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 34bd819e38..210483d4e4 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -9465,6 +9465,13 @@ static abi_long do_syscall1(void *cpu_env, int num, 
abi_long arg1,
              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;
@@ -9478,11 +9485,6 @@ static abi_long do_syscall1(void *cpu_env, int num, 
abi_long arg1,
                  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;