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

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

When the O_PATH emulation fails override the errno value to EBADF
instead of retaining the one from getxattr(2)/setxattr(2).

For example in the case of no procfs being mounted, e.g. inside of a
chroot, getxattr(2)/setxattr(2) fail with ENOENT.  This is confusing to
the caller as it seems 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>
---
 libselinux/src/fgetfilecon.c | 8 +++++---
 libselinux/src/fsetfilecon.c | 8 +++++---
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/libselinux/src/fgetfilecon.c b/libselinux/src/fgetfilecon.c
index baf38ec1..4c440df3 100644
--- a/libselinux/src/fgetfilecon.c
+++ b/libselinux/src/fgetfilecon.c
@@ -10,7 +10,7 @@
 
 static ssize_t fgetxattr_wrapper(int fd, const char *name, void *value, size_t size) {
 	char buf[40];
-	int fd_flag, saved_errno = errno;
+	int fd_flag;
 	ssize_t ret;
 
 	ret = fgetxattr(fd, name, value, size);
@@ -25,8 +25,10 @@ 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 = EBADF;
+	return ret;
 }
 
 int fgetfilecon_raw(int fd, char ** context)
diff --git a/libselinux/src/fsetfilecon.c b/libselinux/src/fsetfilecon.c
index be821c7a..374dc627 100644
--- a/libselinux/src/fsetfilecon.c
+++ b/libselinux/src/fsetfilecon.c
@@ -10,7 +10,7 @@
 
 static int fsetxattr_wrapper(int fd, const char* name, const void* value, size_t size, int flags) {
 	char buf[40];
-	int rc, fd_flag, saved_errno = errno;
+	int rc, fd_flag;
 
 	rc = fsetxattr(fd, name, value, size, flags);
 	if (rc == 0 || errno != EBADF)
@@ -24,8 +24,10 @@ 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 = EBADF;
+	return rc;
 }
 
 int fsetfilecon_raw(int fd, const char * context)
-- 
2.36.1