On 7/25/22 09:28, Rainer Müller wrote:
For certain paths in /proc, the open syscall is intercepted and the
returned file descriptor points to a temporary file with emulated
contents.
If TMPDIR is not accessible or writable for the current user (for
example in a read-only mounted chroot or container) tools such as ps
from procps may fail unexpectedly. Trying to read one of these paths
such as /proc/self/stat would return an error such as ENOENT or EROFS.
To relax the requirement on a writable TMPDIR, use memfd_create()
instead to create an anonymous file and return its file descriptor.
Signed-off-by: Rainer Müller <rai...@codingfarm.de>
---
linux-user/syscall.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 991b85e6b4..3e4af930ad 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -8265,9 +8265,11 @@ static int do_openat(CPUArchState *cpu_env, int dirfd,
const char *pathname, int
}
if (fake_open->filename) {
+ int fd, r;
+
+#ifndef CONFIG_MEMFD
const char *tmpdir;
char filename[PATH_MAX];
- int fd, r;
/* create temporary file to map stat to */
tmpdir = getenv("TMPDIR");
@@ -8279,6 +8281,12 @@ static int do_openat(CPUArchState *cpu_env, int dirfd,
const char *pathname, int
return fd;
}
unlink(filename);
+#else
+ fd = memfd_create("qemu-open", 0);
+ if (fd < 0) {
+ return fd;
+ }
+#endif
Even without CONFIG_MEMFD, we will have the memfd_create function available in
util/.
I think you should drop the ifdefs like so:
#include "qemu/memfd.h"
fd = memfd_create(...);
if (fd < 0) {
if (errno != ENOSYS) {
return fd;
}
// tmpdir fallback
}
r~
