Commit 82ae60c8b5 for qemu.org

commit 82ae60c8b5cb98d610056a1e2d0ba72e9ef7907c
Author: Jean-Christian CÎRSTEA <jean.christian.cirstea@gmail.com>
Date:   Mon Dec 29 14:14:16 2025 +0200

    linux-user: allow null `pathname` for statx()/fstatat()

    Since Linux 6.11, the path argument may be NULL.

    Before this patch, qemu-*-linux-user failed with EFAULT when `pathname` was
    specified as NULL, even for Linux kernel hosts > 6.10. This patch fixes this
    issue by checking whether `arg2` is 0. If so, don't return EFAULT, but instead
    perform the appropiate syscall and let the host's kernel handle null `pathname`.

    Cc: qemu-stable@nongnu.org
    Signed-off-by: Jean-Christian CÎRSTEA <jean.christian.cirstea@gmail.com>
    Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
    Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
    Message-ID: <20251229121416.2209295-1-jean.christian.cirstea@gmail.com>

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 2060e561a2..ee7c34027e 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -12141,9 +12141,13 @@ static abi_long do_syscall1(CPUArchState *cpu_env, int num, abi_long arg1,
             int dirfd = arg1;
             int flags = arg3;

-            p = lock_user_string(arg2);
-            if (p == NULL) {
-                return -TARGET_EFAULT;
+            p = NULL;
+            /* Since Linux 6.11, the path argument may be NULL */
+            if (arg2 != 0) {
+                p = lock_user_string(arg2);
+                if (p == NULL) {
+                    return -TARGET_EFAULT;
+                }
             }
 #if defined(__NR_statx)
             {