From: Ashish Sangwan Subject: [PATCH] e4defrag: Fix segfault when /etc/mtab is empty Date: Thu, 18 Oct 2012 12:06:14 +0530 Message-ID: <1350542174-11565-1-git-send-email-ashish.sangwan2@gmail.com> Cc: sandeen@redhat.com, linux-ext4@vger.kernel.org, Ashish Sangwan , Namjae Jeon To: tytso@mit.edu Return-path: Received: from mail-pa0-f46.google.com ([209.85.220.46]:58643 "EHLO mail-pa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752027Ab2JRGgp (ORCPT ); Thu, 18 Oct 2012 02:36:45 -0400 Received: by mail-pa0-f46.google.com with SMTP id hz1so7987884pad.19 for ; Wed, 17 Oct 2012 23:36:45 -0700 (PDT) Sender: linux-ext4-owner@vger.kernel.org List-ID: Currently, e4defrag will not work on machines where /etc/mtab is not present OR is empty. This patch does 2 things: a) For obtaining mounted FS info, first we try to scan /proc/mounts, if failed to access this file, try with /etc/mtab. b) In function is_ext4, check if the varibale "mnt_type" is null before calling strcmp, otherwise segfault would occur. Signed-off-by: Ashish Sangwan Signed-off-by: Namjae Jeon --- misc/e4defrag.8.in | 6 +++++- misc/e4defrag.c | 26 ++++++++++++++++---------- 2 files changed, 21 insertions(+), 11 deletions(-) diff --git a/misc/e4defrag.8.in b/misc/e4defrag.8.in index 75e1bc9..a5401dc 100644 --- a/misc/e4defrag.8.in +++ b/misc/e4defrag.8.in @@ -31,7 +31,11 @@ reduces fragmentation of all files in it. If is a device, .B e4defrag gets the mount point of it and reduces fragmentation of all files in this mount -point. +point. Mount information is obtained by reading +.B /proc/mounts. +If this file is not accessible, e4defrag will try to get required +information from +.B /etc/mtab. .SH OPTIONS .TP .B \-c diff --git a/misc/e4defrag.c b/misc/e4defrag.c index 4b31d03..285d594 100644 --- a/misc/e4defrag.c +++ b/misc/e4defrag.c @@ -123,6 +123,7 @@ #define NGMSG_FILE_OPEN "Failed to open" #define NGMSG_FILE_UNREG "File is not regular file" #define NGMSG_LOST_FOUND "Can not process \"lost+found\"" +#define _PATH_PROC_MOUNTS "/proc/mounts" /* Data type for filesystem-wide blocks number */ typedef unsigned long long ext4_fsblk_t; @@ -262,10 +263,8 @@ static int fallocate64(int fd, int mode, loff_t offset, loff_t len) * @dir_path_len: the length of directory. */ static int get_mount_point(const char *devname, char *mount_point, - int dir_path_len) + int dir_path_len, const char *mtab) { - /* Refer to /etc/mtab */ - const char *mtab = MOUNTED; FILE *fp = NULL; struct mntent *mnt = NULL; struct stat64 sb; @@ -278,7 +277,7 @@ static int get_mount_point(const char *devname, char *mount_point, fp = setmntent(mtab, "r"); if (fp == NULL) { - perror("Couldn't access /etc/mtab"); + printf("Couldn't access %s\n", mtab); return -1; } @@ -313,14 +312,12 @@ static int get_mount_point(const char *devname, char *mount_point, * * @file: the file's name. */ -static int is_ext4(const char *file, char *devname) +static int is_ext4(const char *file, char *devname, const char *mtab) { int maxlen = 0; int len, ret; FILE *fp = NULL; char *mnt_type = NULL; - /* Refer to /etc/mtab */ - const char *mtab = MOUNTED; char file_path[PATH_MAX + 1]; struct mntent *mnt = NULL; struct statfs64 fsbuf; @@ -345,7 +342,7 @@ static int is_ext4(const char *file, char *devname) fp = setmntent(mtab, "r"); if (fp == NULL) { - perror("Couldn't access /etc/mtab"); + printf("Couldn't access %s", mtab); return -1; } @@ -374,6 +371,10 @@ static int is_ext4(const char *file, char *devname) } endmntent(fp); + if (mnt_type == NULL) { + printf("Could not get mount information from %s\n", mtab); + return -1; + } if (strcmp(mnt_type, FS_EXT4) == 0) { FREE(mnt_type); return 0; @@ -1724,6 +1725,7 @@ int main(int argc, char *argv[]) int success_flag = 0; char dir_name[PATH_MAX + 1]; char dev_name[PATH_MAX + 1]; + char *mtab = NULL; struct stat64 buf; ext2_filsys fs = NULL; @@ -1743,6 +1745,10 @@ int main(int argc, char *argv[]) goto out; } } + if (access(_PATH_PROC_MOUNTS, R_OK) == 0) + mtab = _PATH_PROC_MOUNTS; + else + mtab = _PATH_MOUNTED; if (argc == optind) goto out; @@ -1797,7 +1803,7 @@ int main(int argc, char *argv[]) if (S_ISBLK(buf.st_mode)) { /* Block device */ strncpy(dev_name, argv[i], strnlen(argv[i], PATH_MAX)); - if (get_mount_point(argv[i], dir_name, PATH_MAX) < 0) + if (get_mount_point(argv[i], dir_name, PATH_MAX, mtab) < 0) continue; if (lstat64(dir_name, &buf) < 0) { perror(NGMSG_FILE_INFO); @@ -1833,7 +1839,7 @@ int main(int argc, char *argv[]) * filesystem type checked in get_mount_point() */ if (arg_type == FILENAME || arg_type == DIRNAME) { - if (is_ext4(argv[i], dev_name) < 0) + if (is_ext4(argv[i], dev_name, mtab) < 0) continue; if (realpath(argv[i], dir_name) == NULL) { perror("Couldn't get full path"); -- 1.7.11.4