From 5d238002ff22241a7d04608102a2182aa74d2b69 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