[PATCH v2 2/2] linux-user/main: Check errno when getting AT_EXECFD

[Vivian Wang]

It's possible for AT_EXECFD to end up with a valid value of 0. Check
errno when using qemu_getauxval instead of return value to handle this
case.

Not handling this case leads to a confusing condition where the
executable ends up as fd 0, i.e. stdin.

Signed-off-by: Vivian Wang <uwu@dram.page>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Fixes: 0b959cf5e4cc ("linux-user: Use qemu_getauxval for AT_EXECFD")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2448
---
 linux-user/main.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/linux-user/main.c b/linux-user/main.c
index 7d3cf45fa9..8143a0d4b0 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -755,8 +755,9 @@ int main(int argc, char **argv, char **envp)
     /*
      * Manage binfmt-misc open-binary flag
      */
+    errno = 0;
     execfd = qemu_getauxval(AT_EXECFD);
-    if (execfd == 0) {
+    if (errno != 0) {
         execfd = open(exec_path, O_RDONLY);
         if (execfd < 0) {
             printf("Error while loading %s: %s\n", exec_path, strerror(errno));
-- 
2.45.1