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2.34-6: mountinfo issue

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This commit is contained in:
Karel Zak 2019-09-13 09:53:00 +02:00
parent 83243ee93c
commit 707076abd5
2 changed files with 399 additions and 1 deletions
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383
libmount-improve-mountinfo-reliability.patch Normal file
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@ -0,0 +1,383 @@
From 32fe4f1dd8fbc104bd848e24de613122947f095a Mon Sep 17 00:00:00 2001
From: Karel Zak <kzak@redhat.com>
Date: Wed, 28 Aug 2019 15:47:16 +0200
Subject: [PATCH] libmount: improve mountinfo reliability
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
The standard way how we read mount table is not reliable because
during the read() syscalls the table may be modified by some another
process. The changes in the table is possible to detect by poll()
event, and in this case it seems better to lseek to the begin of the file
and read it again. It's expensive, but better than races...
This patch does not modify mountinfo parser, but it reads all file to
memory (by read()+poll()) and than it creates memory stream
from the buffer and use it rather than a regular file stream.
It means the parser is still possible to use for normal files
(e.g. fstab) as well as for mountinfo and it's also portable to
systems where for some reason is no fmemopen().
Addresses: https://github.com/systemd/systemd/issues/10872
Addresses: https://bugzilla.redhat.com/show_bug.cgi?id=1751447
Upstream: http://github.com/karelzak/util-linux/commit/e4925f591c1bfb83719418b56b952830d15b77eb
Upstream: http://github.com/karelzak/util-linux/commit/ee551c909f95437fd9fcd162f398c069d0ce9720
Reported-by: Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>
Signed-off-by: Karel Zak <kzak@redhat.com>
---
diff -up util-linux-2.34/configure.ac.kzak util-linux-2.34/configure.ac
--- util-linux-2.34/configure.ac.kzak 2019-06-14 12:34:02.892209368 +0200
+++ util-linux-2.34/configure.ac 2019-09-13 09:19:54.155419473 +0200
@@ -466,6 +466,7 @@ AC_CHECK_FUNCS([ \
err \
errx \
explicit_bzero \
+ fmemopen \
fsync \
utimensat \
getdomainname \
diff -up util-linux-2.34/libmount/src/mountP.h.kzak util-linux-2.34/libmount/src/mountP.h
--- util-linux-2.34/libmount/src/mountP.h.kzak 2019-05-09 14:15:40.637552762 +0200
+++ util-linux-2.34/libmount/src/mountP.h 2019-09-13 09:19:54.155419473 +0200
@@ -97,6 +97,7 @@ extern int mnt_valid_tagname(const char
extern int append_string(char **a, const char *b);
extern const char *mnt_statfs_get_fstype(struct statfs *vfs);
+extern int is_procfs_fd(int fd);
extern int is_file_empty(const char *name);
extern int mnt_is_readonly(const char *path)
@@ -121,6 +122,7 @@ extern void mnt_free_filesystems(char **
extern char *mnt_get_kernel_cmdline_option(const char *name);
extern int mnt_stat_mountpoint(const char *target, struct stat *st);
+extern FILE *mnt_get_procfs_memstream(int fd, char **membuf);
/* tab.c */
extern int is_mountinfo(struct libmnt_table *tb);
diff -up util-linux-2.34/libmount/src/tab_parse.c.kzak util-linux-2.34/libmount/src/tab_parse.c
--- util-linux-2.34/libmount/src/tab_parse.c.kzak 2019-05-09 14:15:40.638552755 +0200
+++ util-linux-2.34/libmount/src/tab_parse.c 2019-09-13 09:19:54.156419468 +0200
@@ -698,15 +698,7 @@ static int kernel_fs_postparse(struct li
return rc;
}
-/**
- * mnt_table_parse_stream:
- * @tb: tab pointer
- * @f: file stream
- * @filename: filename used for debug and error messages
- *
- * Returns: 0 on success, negative number in case of error.
- */
-int mnt_table_parse_stream(struct libmnt_table *tb, FILE *f, const char *filename)
+static int __table_parse_stream(struct libmnt_table *tb, FILE *f, const char *filename)
{
int rc = -1;
int flags = 0;
@@ -781,6 +773,40 @@ err:
}
/**
+ * mnt_table_parse_stream:
+ * @tb: tab pointer
+ * @f: file stream
+ * @filename: filename used for debug and error messages
+ *
+ * Returns: 0 on success, negative number in case of error.
+ */
+int mnt_table_parse_stream(struct libmnt_table *tb, FILE *f, const char *filename)
+{
+ int fd, rc;
+ FILE *memf = NULL;
+ char *membuf = NULL;
+
+ /*
+ * For /proc/#/{mountinfo,mount} we read all file to memory and use it
+ * as memory stream. For more details see mnt_read_procfs_file().
+ */
+ if ((fd = fileno(f)) >= 0
+ && (tb->fmt == MNT_FMT_GUESS ||
+ tb->fmt == MNT_FMT_MOUNTINFO ||
+ tb->fmt == MNT_FMT_MTAB)
+ && is_procfs_fd(fd)
+ && (memf = mnt_get_procfs_memstream(fd, &membuf))) {
+
+ rc = __table_parse_stream(tb, memf, filename);
+ fclose(memf);
+ free(membuf);
+ } else
+ rc = __table_parse_stream(tb, f, filename);
+
+ return rc;
+}
+
+/**
* mnt_table_parse_file:
* @tb: tab pointer
* @filename: file
@@ -795,18 +821,49 @@ err:
int mnt_table_parse_file(struct libmnt_table *tb, const char *filename)
{
FILE *f;
- int rc;
+ int rc, fd = -1;
if (!filename || !tb)
return -EINVAL;
- f = fopen(filename, "r" UL_CLOEXECSTR);
+ /*
+ * Try to use read()+poll() to realiably read all
+ * /proc/#/{mount,mountinfo} file to memory
+ */
+ if (tb->fmt != MNT_FMT_SWAPS
+ && strncmp(filename, "/proc/", 6) == 0) {
+
+ FILE *memf;
+ char *membuf = NULL;
+
+ fd = open(filename, O_RDONLY|O_CLOEXEC);
+ if (fd < 0) {
+ rc = -errno;
+ goto done;
+ }
+ memf = mnt_get_procfs_memstream(fd, &membuf);
+ if (memf) {
+ rc = __table_parse_stream(tb, memf, filename);
+
+ fclose(memf);
+ free(membuf);
+ close(fd);
+ goto done;
+ }
+ /* else fallback to fopen/fdopen() */
+ }
+
+ if (fd >= 0)
+ f = fdopen(fd, "r" UL_CLOEXECSTR);
+ else
+ f = fopen(filename, "r" UL_CLOEXECSTR);
+
if (f) {
- rc = mnt_table_parse_stream(tb, f, filename);
+ rc = __table_parse_stream(tb, f, filename);
fclose(f);
} else
rc = -errno;
-
+done:
DBG(TAB, ul_debugobj(tb, "parsing done [filename=%s, rc=%d]", filename, rc));
return rc;
}
@@ -863,7 +920,7 @@ static int __mnt_table_parse_dir(struct
f = fopen_at(dd, d->d_name, O_RDONLY|O_CLOEXEC, "r" UL_CLOEXECSTR);
if (f) {
- mnt_table_parse_stream(tb, f, d->d_name);
+ __table_parse_stream(tb, f, d->d_name);
fclose(f);
}
}
@@ -904,7 +961,7 @@ static int __mnt_table_parse_dir(struct
f = fopen_at(dirfd(dir), d->d_name,
O_RDONLY|O_CLOEXEC, "r" UL_CLOEXECSTR);
if (f) {
- mnt_table_parse_stream(tb, f, d->d_name);
+ __table_parse_stream(tb, f, d->d_name);
fclose(f);
}
}
diff -up util-linux-2.34/libmount/src/utils.c.kzak util-linux-2.34/libmount/src/utils.c
--- util-linux-2.34/libmount/src/utils.c.kzak 2019-06-13 13:26:04.946525187 +0200
+++ util-linux-2.34/libmount/src/utils.c 2019-09-13 09:19:54.157419462 +0200
@@ -19,6 +19,7 @@
#include <fcntl.h>
#include <pwd.h>
#include <grp.h>
+#include <poll.h>
#include <blkid.h>
#include "strutils.h"
@@ -424,6 +425,12 @@ const char *mnt_statfs_get_fstype(struct
return NULL;
}
+int is_procfs_fd(int fd)
+{
+ struct statfs sfs;
+
+ return fstatfs(fd, &sfs) == 0 && sfs.f_type == STATFS_PROC_MAGIC;
+}
/**
* mnt_match_fstype:
@@ -1140,8 +1147,158 @@ done:
return 1;
}
+#if defined(HAVE_FMEMOPEN) || defined(TEST_PROGRAM)
+
+/*
+ * This function tries to minimize possible races when we read
+ * /proc/#/{mountinfo,mount} files.
+ *
+ * The idea is to minimize number of read()s and check by poll() that during
+ * the read the mount table has not been modified. If yes, than re-read it
+ * (with some limitations to avoid never ending loop).
+ *
+ * Returns: <0 error, 0 success, 1 too many attempts
+ */
+static int read_procfs_file(int fd, char **buf, size_t *bufsiz)
+{
+ size_t bufmax = 0;
+ int rc = 0, tries = 0, ninters = 0;
+ char *bufptr = NULL;;
+
+ assert(buf);
+ assert(bufsiz);
+
+ *bufsiz = 0;
+ *buf = NULL;
+
+ do {
+ ssize_t ret;
+
+ if (!bufptr || bufmax == *bufsiz) {
+ char *tmp;
+
+ bufmax = bufmax ? bufmax * 2 : (16 * 1024);
+ tmp = realloc(*buf, bufmax);
+ if (!tmp)
+ break;
+ *buf = tmp;
+ bufptr = tmp + *bufsiz;
+ }
+
+ errno = 0;
+ ret = read(fd, bufptr, bufmax - *bufsiz);
+
+ if (ret < 0) {
+ /* error */
+ if ((errno == EAGAIN || errno == EINTR) && (ninters++ < 5)) {
+ xusleep(200000);
+ continue;
+ }
+ break;
+
+ } else if (ret > 0) {
+ /* success -- verify no event during read */
+ struct pollfd fds[] = {
+ { .fd = fd, .events = POLLPRI }
+ };
+
+ rc = poll(fds, 1, 0);
+ if (rc < 0)
+ break; /* poll() error */
+ if (rc > 0) {
+ /* event -- read all again */
+ if (lseek(fd, 0, SEEK_SET) != 0)
+ break;
+ *bufsiz = 0;
+ bufptr = *buf;
+ tries++;
+
+ if (tries > 10)
+ /* busy system? -- wait */
+ xusleep(10000);
+ continue;
+ }
+
+ /* successful read() without active poll() */
+ (*bufsiz) += (size_t) ret;
+ bufptr += ret;
+ tries = ninters = 0;
+ } else {
+ /* end-of-file */
+ goto success;
+ }
+ } while (tries <= 100);
+
+ rc = errno ? -errno : 1;
+ free(*buf);
+ return rc;
+
+success:
+ return 0;
+}
+
+/*
+ * Create FILE stream for data from read_procfs_file()
+ */
+FILE *mnt_get_procfs_memstream(int fd, char **membuf)
+{
+ FILE *memf;
+ size_t sz = 0;
+ off_t cur;
+
+ /* in case of error, rewind to the original position */
+ cur = lseek(fd, 0, SEEK_CUR);
+
+ if (read_procfs_file(fd, membuf, &sz) == 0
+ && sz > 0
+ && (memf = fmemopen(*membuf, sz, "r")))
+ return memf;
+
+ /* error */
+ lseek(fd, cur, SEEK_SET);
+ return NULL;
+}
+#else
+FILE *mnt_get_procfs_memstream(int fd __attribute((__unused__)),
+ char **membuf __attribute((__unused__)))
+{
+ return NULL;
+}
+#endif /* HAVE_FMEMOPEN */
+
#ifdef TEST_PROGRAM
+static int test_proc_read(struct libmnt_test *ts, int argc, char *argv[])
+{
+ char *buf = NULL;
+ char *filename = argv[1];
+ size_t bufsiz = 0;
+ int rc = 0, fd = open(filename, O_RDONLY);
+
+ if (fd <= 0) {
+ warn("%s: cannot open", filename);
+ return -errno;
+ }
+
+ rc = read_procfs_file(fd, &buf, &bufsiz);
+ close(fd);
+
+ switch (rc) {
+ case 0:
+ fwrite(buf, 1, bufsiz, stdout);
+ free(buf);
+ break;
+ case 1:
+ warnx("too many attempts");
+ break;
+ default:
+ warn("%s: cannot read", filename);
+ break;
+ }
+
+ return rc;
+}
+
static int test_match_fstype(struct libmnt_test *ts, int argc, char *argv[])
{
char *type = argv[1];
@@ -1323,6 +1480,7 @@ int main(int argc, char *argv[])
{ "--guess-root", test_guess_root, "[<maj:min>]" },
{ "--mkdir", test_mkdir, "<path>" },
{ "--statfs-type", test_statfs_type, "<path>" },
+ { "--read-procfs", test_proc_read, "<path>" },
{ NULL }
};

17
util-linux.spec
View File

@ -2,7 +2,7 @@
Summary: A collection of basic system utilities
Name: util-linux
Version: 2.34
Release: 5%{?dist}
Release: 6%{?dist}
License: GPLv2 and GPLv2+ and LGPLv2+ and BSD with advertising and Public Domain
URL: http://en.wikipedia.org/wiki/Util-linux
@ -41,6 +41,10 @@ BuildRequires: gcc
%ifarch ppc64le
BuildRequires: librtas-devel
%endif
BuildRequires: autoconf
BuildRequires: automake
BuildRequires: libtool
BuildRequires: bison
### Sources
Source0: ftp://ftp.kernel.org/pub/linux/utils/util-linux/v%{upstream_major}/util-linux-%{upstream_version}.tar.xz
@ -104,6 +108,8 @@ Patch0: 2.28-login-lastlog-create.patch
# 1751290 - regression: lsblk not showing PKNAME in f31+
Patch1: lsblk-force-to-print-PKNAME-for-partition.patch
# https://github.com/systemd/systemd/issues/10872
Patch2: libmount-improve-mountinfo-reliability.patch
%description
The util-linux package contains a large variety of low-level system
@ -273,6 +279,12 @@ chfn and chsh utilities with dependence on libuser
%build
unset LINGUAS || :
# unfortunately, we did changes to build-system
./autogen.sh
# we modify .po files by RHEL patches
rm -f po/stamp*
export CFLAGS="-D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 $RPM_OPT_FLAGS"
export SUID_CFLAGS="-fpie"
export SUID_LDFLAGS="-pie -Wl,-z,relro -Wl,-z,now"
@ -922,6 +934,9 @@ fi
%{_libdir}/python*/site-packages/libmount/
%changelog
* Fri Sep 13 2019 Karel Zak <kzak@redhat.com> - 2.34-6
- fix https://github.com/systemd/systemd/issues/10872
* Thu Sep 12 2019 Karel Zak <kzak@redhat.com> - 2.34-5
- fix #1751290 - regression: lsblk not showing PKNAME in f31+