From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-Id: <20130518021647.546880307@goodmis.org> Date: Fri, 17 May 2013 22:16:33 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Li Zefan , Ming Lei , Greg Kroah-Hartman Subject: [ 036/136 ] sysfs: fix use after free in case of concurrent read/write and readdir References: <20130518021557.139113314@goodmis.org> Content-Disposition: inline; filename=0036-sysfs-fix-use-after-free-in-case-of-concurrent-read-.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.6.11.4 stable review patch. If anyone has any objections, please let me know. ------------------ From: Ming Lei [ Upstream commit f7db5e7660b122142410dcf36ba903c73d473250 ] The inode->i_mutex isn't hold when updating filp->f_pos in read()/write(), so the filp->f_pos might be read as 0 or 1 in readdir() when there is concurrent read()/write() on this same file, then may cause use after free in readdir(). The bug can be reproduced with Li Zefan's test code on the link: https://patchwork.kernel.org/patch/2160771/ This patch fixes the use after free under this situation. Cc: stable Reported-by: Li Zefan Signed-off-by: Ming Lei Signed-off-by: Greg Kroah-Hartman Signed-off-by: Steven Rostedt --- fs/sysfs/dir.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c index 4b93159..76f38eb 100644 --- a/fs/sysfs/dir.c +++ b/fs/sysfs/dir.c @@ -1012,6 +1012,7 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir) enum kobj_ns_type type; const void *ns; ino_t ino; + loff_t off; type = sysfs_ns_type(parent_sd); ns = sysfs_info(dentry->d_sb)->ns[type]; @@ -1034,6 +1035,7 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir) return 0; } mutex_lock(&sysfs_mutex); + off = filp->f_pos; for (pos = sysfs_dir_pos(ns, parent_sd, filp->f_pos, pos); pos; pos = sysfs_dir_next_pos(ns, parent_sd, filp->f_pos, pos)) { @@ -1045,19 +1047,24 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir) len = strlen(name); ino = pos->s_ino; type = dt_type(pos); - filp->f_pos = pos->s_hash; + off = filp->f_pos = pos->s_hash; filp->private_data = sysfs_get(pos); mutex_unlock(&sysfs_mutex); - ret = filldir(dirent, name, len, filp->f_pos, ino, type); + ret = filldir(dirent, name, len, off, ino, type); mutex_lock(&sysfs_mutex); if (ret < 0) break; } mutex_unlock(&sysfs_mutex); - if ((filp->f_pos > 1) && !pos) { /* EOF */ - filp->f_pos = INT_MAX; + + /* don't reference last entry if its refcount is dropped */ + if (!pos) { filp->private_data = NULL; + + /* EOF and not changed as 0 or 1 in read/write path */ + if (off == filp->f_pos && off > 1) + filp->f_pos = INT_MAX; } return 0; } -- 1.7.10.4