[libc-commits] [libc] [libc] Fix sendmsg iovec unpoisoning (PR #115057)

[Michael Jones via libc-commits]

https://github.com/michaelrj-google created https://github.com/llvm/llvm-project/pull/115057

The unpoisoning for sendmsg had a typo where it would not unpoison all
of the elements in the iovec, causing msan errors. This patch fixes
that.


>From 357f0fd1547573e0743b8984c8392725c4d36e0a Mon Sep 17 00:00:00 2001
From: Michael Jones <michaelrj at google.com>
Date: Tue, 5 Nov 2024 12:24:46 -0800
Subject: [PATCH] [libc] Fix sendmsg iovec unpoisoning

The unpoisoning for sendmsg had a typo where it would not unpoison all
of the elements in the iovec, causing msan errors. This patch fixes
that.
---
 libc/src/sys/socket/linux/recvmsg.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/libc/src/sys/socket/linux/recvmsg.cpp b/libc/src/sys/socket/linux/recvmsg.cpp
index 60bbc84877b850..43929da87e16d2 100644
--- a/libc/src/sys/socket/linux/recvmsg.cpp
+++ b/libc/src/sys/socket/linux/recvmsg.cpp
@@ -40,9 +40,11 @@ LLVM_LIBC_FUNCTION(ssize_t, recvmsg,
   }
 
   // Unpoison the msghdr, as well as all its components.
+  MSAN_UNPOISON(msg, sizeof(struct msghdr));
   MSAN_UNPOISON(msg->msg_name, msg->msg_namelen);
+
   for (size_t i = 0; i < msg->msg_iovlen; ++i) {
-    MSAN_UNPOISON(msg->msg_iov->iov_base, msg->msg_iov->iov_len);
+    MSAN_UNPOISON(msg->msg_iov[i].iov_base, msg->msg_iov[i].iov_len);
   }
   MSAN_UNPOISON(msg->msg_control, msg->msg_controllen);