9p: do not trust pdu content for stat item size

v9fs_dir_readdir() could deadloop if a struct was sent with a size set
to -2

Link: http://lkml.kernel.org/r/1536134432-11997-1-git-send-email-asmadeus@codewreck.org
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=88021
Signed-off-by: Gertjan Halkes <gertjan@google.com>
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>

diff --git a/fs/9p/vfs_dir.c b/fs/9p/vfs_dir.c
index 48db9a9f13f9e1800a81fcd992c69bcb0aac069c..cb6c4031af552b010c2e8ff5469b9088c769b3b7 100644 (file)
--- a/fs/9p/vfs_dir.c
+++ b/fs/9p/vfs_dir.c
@@ -105,7 +105,6 @@ static int v9fs_dir_readdir(struct file *file, struct dir_context *ctx)
        int err = 0;
        struct p9_fid *fid;
        int buflen;
-       int reclen = 0;
        struct p9_rdir *rdir;
        struct kvec kvec;
 
@@ -138,11 +137,10 @@ static int v9fs_dir_readdir(struct file *file, struct dir_context *ctx)
                while (rdir->head < rdir->tail) {
                        err = p9stat_read(fid->clnt, rdir->buf + rdir->head,
                                          rdir->tail - rdir->head, &st);
-                       if (err) {
+                       if (err <= 0) {
                                p9_debug(P9_DEBUG_VFS, "returned %d\n", err);
                                return -EIO;
                        }
-                       reclen = st.size+2;
 
                        over = !dir_emit(ctx, st.name, strlen(st.name),
                                         v9fs_qid2ino(&st.qid), dt_type(&st));
@@ -150,8 +148,8 @@ static int v9fs_dir_readdir(struct file *file, struct dir_context *ctx)
                        if (over)
                                return 0;
 
-                       rdir->head += reclen;
-                       ctx->pos += reclen;
+                       rdir->head += err;
+                       ctx->pos += err;
                }
        }
 }

diff --git a/net/9p/protocol.c b/net/9p/protocol.c
index ee32bbf12675690848a60b3b6ca0a6f87e9e945e..b4d80c533f897915fbb980fc13638f859f75acf3 100644 (file)
--- a/net/9p/protocol.c
+++ b/net/9p/protocol.c
@@ -571,9 +571,10 @@ int p9stat_read(struct p9_client *clnt, char *buf, int len, struct p9_wstat *st)
        if (ret) {
                p9_debug(P9_DEBUG_9P, "<<< p9stat_read failed: %d\n", ret);
                trace_9p_protocol_dump(clnt, &fake_pdu);
+               return ret;
        }
 
-       return ret;
+       return fake_pdu.offset;
 }
 EXPORT_SYMBOL(p9stat_read);