6.12-stable review patch. If anyone has any objections, please let me know.
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From: Sean Heelan seanheelan@gmail.com
commit 36991c1ccde2d5a521577c448ffe07fcccfe104d upstream.
A use-after-free is possible if one thread destroys the file via __ksmbd_close_fd while another thread holds a reference to it. The existing checks on fp->refcount are not sufficient to prevent this.
The fix takes ft->lock around the section which removes the file from the file table. This prevents two threads acquiring the same file pointer via __close_file_table_ids, as well as the other functions which retrieve a file from the IDR and which already use this same lock.
Cc: stable@vger.kernel.org Signed-off-by: Sean Heelan seanheelan@gmail.com Acked-by: Namjae Jeon linkinjeon@kernel.org Signed-off-by: Steve French stfrench@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/smb/server/vfs_cache.c | 33 ++++++++++++++++++++++++++------- 1 file changed, 26 insertions(+), 7 deletions(-)
--- a/fs/smb/server/vfs_cache.c +++ b/fs/smb/server/vfs_cache.c @@ -661,21 +661,40 @@ __close_file_table_ids(struct ksmbd_file bool (*skip)(struct ksmbd_tree_connect *tcon, struct ksmbd_file *fp)) { - unsigned int id; - struct ksmbd_file *fp; - int num = 0; + struct ksmbd_file *fp; + unsigned int id = 0; + int num = 0;
- idr_for_each_entry(ft->idr, fp, id) { - if (skip(tcon, fp)) + while (1) { + write_lock(&ft->lock); + fp = idr_get_next(ft->idr, &id); + if (!fp) { + write_unlock(&ft->lock); + break; + } + + if (skip(tcon, fp) || + !atomic_dec_and_test(&fp->refcount)) { + id++; + write_unlock(&ft->lock); continue; + }
set_close_state_blocked_works(fp); + idr_remove(ft->idr, fp->volatile_id); + fp->volatile_id = KSMBD_NO_FID; + write_unlock(&ft->lock); + + down_write(&fp->f_ci->m_lock); + list_del_init(&fp->node); + up_write(&fp->f_ci->m_lock);
- if (!atomic_dec_and_test(&fp->refcount)) - continue; __ksmbd_close_fd(ft, fp); + num++; + id++; } + return num; }