Re: [PATCH v2 1/2] linux-user: rt_sigprocmask, check read perms first

[Laurent Vivier]

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

From: Shu-Chun Weng <s...@google.com>

Linux kernel does it this way (checks read permission before validating `how`)
and the latest version of ABSL's `AddressIsReadable()` depends on this
behavior.

c.f.  
https://github.com/torvalds/linux/blob/9539ba4308ad5bdca6cb41c7b73cbb9f796dcdd7/kernel/signal.c#L3147
Reviewed-by: Patrick Venture <vent...@google.com>
Signed-off-by: Shu-Chun Weng <s...@google.com>

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

but you must resend the patch: you are not the author, but you have to add your 
Signed-off-by.
(and now you can add my reviewed-by)

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/SubmittingPatches?id=f6f94e2ab1b33f0082ac22d71f66385a60d8157f#n296

Thanks,
Laurent

---
  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 5950222a77..34bd819e38 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -9508,6 +9508,13 @@ static abi_long do_syscall1(void *cpu_env, int num, 
abi_long arg1,
              }

if (arg2) {

+                p = lock_user(VERIFY_READ, arg2, sizeof(target_sigset_t), 1);
+                if (!p) {
+                    return -TARGET_EFAULT;
+                }
+                target_to_host_sigset(&set, p);
+                unlock_user(p, arg2, 0);
+                set_ptr = &set;
                  switch(how) {
                  case TARGET_SIG_BLOCK:
                      how = SIG_BLOCK;
@@ -9521,11 +9528,6 @@ 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_sigset(&set, p);
-                unlock_user(p, arg2, 0);
-                set_ptr = &set;
              } else {
                  how = 0;
                  set_ptr = NULL;