diff options
| author | Ming Lei <ming.lei@canonical.com> | 2013-04-02 10:12:26 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-04-03 11:09:02 -0700 |
| commit | f7db5e7660b122142410dcf36ba903c73d473250 (patch) | |
| tree | 5385cf0537e4cad0a2896070c45f2b492a74f0ff /fs/sysfs | |
| parent | 0f8b1a0204a12441cddbbf5be31e6338e0b8da1c (diff) | |
| download | lwn-f7db5e7660b122142410dcf36ba903c73d473250.tar.gz lwn-f7db5e7660b122142410dcf36ba903c73d473250.zip | |
sysfs: fix use after free in case of concurrent read/write and readdir
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 <stable@vger.kernel.org>
Reported-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/sysfs')
| -rw-r--r-- | fs/sysfs/dir.c | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c index c6f54abe9852..1bf016b5e88f 100644 --- a/fs/sysfs/dir.c +++ b/fs/sysfs/dir.c @@ -999,6 +999,7 @@ 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]; @@ -1021,6 +1022,7 @@ 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)) { @@ -1032,19 +1034,24 @@ 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; } |