diff options
| author | Ming Lei <ming.lei@canonical.com> | 2013-04-02 10:12:26 +0800 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2013-05-13 15:02:13 +0100 |
| commit | 3a8aad02f417b5aecafdc785c39c0e2259995c69 (patch) | |
| tree | 956423616bd281c99edbb37912c283cca1d3832f /fs | |
| parent | 893bee37f931a600f473801ee1c9c3e2030c2c86 (diff) | |
sysfs: fix use after free in case of concurrent read/write and readdir
commit f7db5e7660b122142410dcf36ba903c73d473250 upstream.
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.
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>
[bwh: Backported to 3.2: file position is child inode number, not hash]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'fs')
| -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 3899e240c29..e756bc4d98a 100644 --- a/fs/sysfs/dir.c +++ b/fs/sysfs/dir.c @@ -977,6 +977,7 @@ 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]; @@ -999,6 +1000,7 @@ 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)) { @@ -1010,19 +1012,24 @@ 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 = ino; + off = filp->f_pos = ino; 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; } |