[PATCH v2] libselinux: set errno to EBADF on O_PATH emulation ENOENT failure

["Christian Göttsche" <cgzones@googlemail.com>]

When the O_PATH emulation fails due to getxattr(2)/setxattr(2) failing
with ENOENT, e.g. because no procfs being available, override the errno
value to EBADF.  This avoids confusion to the caller as it would suggest
the target of the operation does not exist, which is not the case:

    setfiles: Could not set context for /:  No such file or directory

Fixes: a782abf2 ("libselinux: emulate O_PATH support in fgetfilecon/fsetfilecon")
Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
---
v2:
   only override errno on ENOENT
Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
---
 libselinux/src/fgetfilecon.c | 5 ++++-
 libselinux/src/fsetfilecon.c | 5 ++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/libselinux/src/fgetfilecon.c b/libselinux/src/fgetfilecon.c
index baf38ec1..d7051171 100644
--- a/libselinux/src/fgetfilecon.c
+++ b/libselinux/src/fgetfilecon.c
@@ -26,7 +26,10 @@ static ssize_t fgetxattr_wrapper(int fd, const char *name, void *value, size_t s
 
 	snprintf(buf, sizeof(buf), "/proc/self/fd/%d", fd);
 	errno = saved_errno;
-	return getxattr(buf, name, value, size);
+	ret = getxattr(buf, name, value, size);
+	if (ret < 0 && errno == ENOENT)
+		errno = EBADF;
+	return ret;
 }
 
 int fgetfilecon_raw(int fd, char ** context)
diff --git a/libselinux/src/fsetfilecon.c b/libselinux/src/fsetfilecon.c
index be821c7a..19ea15b7 100644
--- a/libselinux/src/fsetfilecon.c
+++ b/libselinux/src/fsetfilecon.c
@@ -25,7 +25,10 @@ static int fsetxattr_wrapper(int fd, const char* name, const void* value, size_t
 
 	snprintf(buf, sizeof(buf), "/proc/self/fd/%d", fd);
 	errno = saved_errno;
-	return setxattr(buf, name, value, size, flags);
+	rc = setxattr(buf, name, value, size, flags);
+	if (rc < 0 && errno == ENOENT)
+		errno = EBADF;
+	return rc;
 }
 
 int fsetfilecon_raw(int fd, const char * context)
-- 
2.36.1