From 945d26162e639fd9ae3a774f1debaaa9511c7919 Mon Sep 17 00:00:00 2001

From: Karel Zak <kzak@redhat.com>

Date: Wed, 8 Nov 2017 16:47:40 +0100

Subject: [PATCH] libmount: fix access() utab write test

The commit c08396c7691e1e6a04b6b45892e7e4612ceed8d7 replaces

open(O_CREATE) with ecaccess(). Unfortunately, another code depends on

the original behavior.

* let's make utab when really necessary rather than in the try_write() test

* __mnt_new_table_from_file() returns NULL if tab-file does not

 exists. This is incorrect for tab_update.c stuff. We need empty table

 in this case.

* we can check /run/mount/ directory for write access if

  eaccess(filename) return ENOENT (because file does not exist)

Addresses: https://bugzilla.redhat.com/show_bug.cgi?id=1499760

Upstream: http://github.com/karelzak/util-linux/commit/06ff935ec3ad2290025b555ff32b590680af565f

Signed-off-by: Karel Zak <kzak@redhat.com>

---

 libmount/src/mountP.h     |  2 +-

 libmount/src/tab_parse.c  | 11 +++++++----

 libmount/src/tab_update.c |  9 +++++----

 libmount/src/utils.c      | 42 +++++++++++++++++++++++++++++++-----------

 4 files changed, 44 insertions(+), 20 deletions(-)

diff --git a/libmount/src/mountP.h b/libmount/src/mountP.h

index 6cabcedeb..8b3f92e17 100644

--- a/libmount/src/mountP.h

+++ b/libmount/src/mountP.h

@@ -278,7 +278,7 @@ struct libmnt_table {

 	struct list_head	ents;	/* list of entries (libmnt_fs) */

 };

-extern struct libmnt_table *__mnt_new_table_from_file(const char *filename, int fmt);

+extern struct libmnt_table *__mnt_new_table_from_file(const char *filename, int fmt, int empty_for_enoent);

 /*

  * Tab file format

diff --git a/libmount/src/tab_parse.c b/libmount/src/tab_parse.c

index 987e671fa..c629c67ad 100644

--- a/libmount/src/tab_parse.c

+++ b/libmount/src/tab_parse.c

@@ -714,7 +714,7 @@ int mnt_table_parse_dir(struct libmnt_table *tb, const char *dirname)

 	return __mnt_table_parse_dir(tb, dirname);

 }

-struct libmnt_table *__mnt_new_table_from_file(const char *filename, int fmt)

+struct libmnt_table *__mnt_new_table_from_file(const char *filename, int fmt, int empty_for_enoent)

 {

 	struct libmnt_table *tb;

 	struct stat st;

@@ -723,7 +723,8 @@ struct libmnt_table *__mnt_new_table_from_file(const char *filename, int fmt)

 	if (!filename)

 		return NULL;

 	if (stat(filename, &st))

-		return NULL;

+		return empty_for_enoent ? mnt_new_table() : NULL;

+

 	tb = mnt_new_table();

 	if (tb) {

 		tb->fmt = fmt;

@@ -748,8 +749,10 @@ struct libmnt_table *__mnt_new_table_from_file(const char *filename, int fmt)

  */

 struct libmnt_table *mnt_new_table_from_file(const char *filename)

 {

-	assert(filename);

-	return __mnt_new_table_from_file(filename, MNT_FMT_GUESS);

+	if (!filename)

+		return NULL;

+

+	return __mnt_new_table_from_file(filename, MNT_FMT_GUESS, 0);

 }

 /**

diff --git a/libmount/src/tab_update.c b/libmount/src/tab_update.c

index 1e7f32be0..5f503cad7 100644

--- a/libmount/src/tab_update.c

+++ b/libmount/src/tab_update.c

@@ -567,6 +567,7 @@ leave:

 	unlink(uq);	/* be paranoid */

 	free(uq);

+	DBG(UPDATE, mnt_debug_h(upd, "%s: done [rc=%d]", upd->filename, rc));

 	return rc;

 }

@@ -600,7 +601,7 @@ static int update_add_entry(struct libmnt_update *upd, struct libmnt_lock *lc)

 		return rc;

 	tb = __mnt_new_table_from_file(upd->filename,

-			upd->userspace_only ? MNT_FMT_UTAB : MNT_FMT_MTAB);

+			upd->userspace_only ? MNT_FMT_UTAB : MNT_FMT_MTAB, 1);

 	if (tb)

 		rc = add_file_entry(tb, upd);

 	if (lc)

@@ -626,7 +627,7 @@ static int update_remove_entry(struct libmnt_update *upd, struct libmnt_lock *lc

 		return rc;

 	tb = __mnt_new_table_from_file(upd->filename,

-			upd->userspace_only ? MNT_FMT_UTAB : MNT_FMT_MTAB);

+			upd->userspace_only ? MNT_FMT_UTAB : MNT_FMT_MTAB, 1);

 	if (tb) {

 		struct libmnt_fs *rem = mnt_table_find_target(tb, upd->target, MNT_ITER_BACKWARD);

 		if (rem) {

@@ -656,7 +657,7 @@ static int update_modify_target(struct libmnt_update *upd, struct libmnt_lock *l

 		return rc;

 	tb = __mnt_new_table_from_file(upd->filename,

-			upd->userspace_only ? MNT_FMT_UTAB : MNT_FMT_MTAB);

+			upd->userspace_only ? MNT_FMT_UTAB : MNT_FMT_MTAB, 1);

 	if (tb) {

 		struct libmnt_fs *cur = mnt_table_find_target(tb,

 				mnt_fs_get_srcpath(upd->fs), MNT_ITER_BACKWARD);

@@ -693,7 +694,7 @@ static int update_modify_options(struct libmnt_update *upd, struct libmnt_lock *

 		return rc;

 	tb = __mnt_new_table_from_file(upd->filename,

-			upd->userspace_only ? MNT_FMT_UTAB : MNT_FMT_MTAB);

+			upd->userspace_only ? MNT_FMT_UTAB : MNT_FMT_MTAB, 1);

 	if (tb) {

 		struct libmnt_fs *cur = mnt_table_find_target(tb,

 					mnt_fs_get_target(fs),

diff --git a/libmount/src/utils.c b/libmount/src/utils.c

index a275d0a0e..fa33bd9a1 100644

--- a/libmount/src/utils.c

+++ b/libmount/src/utils.c

@@ -651,18 +651,37 @@ done:

 	return rc;

 }

-static int try_write(const char *filename)

+static int try_write(const char *filename, const char *directory)

 {

 	int rc = 0;

 	if (!filename)

 		return -EINVAL;

+	DBG(UTILS, mnt_debug("try write %s dir: %s", filename, directory));

+

 #ifdef HAVE_EACCESS

-	if (eaccess(filename, R_OK|W_OK) != 0)

-		rc = -errno;

-#else

+	/* Try eaccess() first, because open() is overkill, may be monitored by

+	 * audit and we don't want to fill logs by our checks...

+	 */

+	if (eaccess(filename, R_OK|W_OK) == 0) {

+		DBG(UTILS, mnt_debug(" access OK"));

+		return 0;

+	} else if (errno != ENOENT) {

+		DBG(UTILS, mnt_debug(" access FAILED"));

+		return -errno;

+	} else if (directory) {

+		/* file does not exist; try if directory is writable */

+		if (eaccess(directory, R_OK|W_OK) != 0)

+			rc = -errno;

+

+		DBG(UTILS, mnt_debug(" access %s [%s]", rc ? "FAILED" : "OK", directory));

+		return rc;

+	} else

+#endif

 	{

+		DBG(UTILS, mnt_debug(" doing open-write test"));

+

 		int fd = open(filename, O_RDWR|O_CREAT|O_CLOEXEC,

 			    S_IWUSR|S_IRUSR|S_IRGRP|S_IROTH);

 		if (fd < 0)

@@ -670,7 +689,6 @@ static int try_write(const char *filename)

 		else

 			close(fd);

 	}

-#endif

 	return rc;

 }

@@ -704,7 +722,7 @@ int mnt_has_regular_mtab(const char **mtab, int *writable)

 		/* file exist */

 		if (S_ISREG(st.st_mode)) {

 			if (writable)

-				*writable = !try_write(filename);

+				*writable = !try_write(filename, NULL);

 			return 1;

 		}

 		goto done;

@@ -712,7 +730,7 @@ int mnt_has_regular_mtab(const char **mtab, int *writable)

 	/* try to create the file */

 	if (writable) {

-		*writable = !try_write(filename);

+		*writable = !try_write(filename, NULL);

 		if (*writable)

 			return 1;

 	}

@@ -750,7 +768,7 @@ int mnt_has_regular_utab(const char **utab, int *writable)

 		/* file exist */

 		if (S_ISREG(st.st_mode)) {

 			if (writable)

-				*writable = !try_write(filename);

+				*writable = !try_write(filename, NULL);

 			return 1;

 		}

 		goto done;	/* it's not regular file */

@@ -767,11 +785,13 @@ int mnt_has_regular_utab(const char **utab, int *writable)

 		rc = mkdir(dirname, S_IWUSR|

 				    S_IRUSR|S_IRGRP|S_IROTH|

 				    S_IXUSR|S_IXGRP|S_IXOTH);

-		free(dirname);

-		if (rc && errno != EEXIST)

+		if (rc && errno != EEXIST) {

+			free(dirname);

 			goto done;			/* probably EACCES */

+		}

-		*writable = !try_write(filename);

+		*writable = !try_write(filename, dirname);

+		free(dirname);

 		if (*writable)

 			return 1;

 	}

-- 

2.13.6