[PATCH 3.18 077/104] 9p: do not trust pdu content for stat item size

Greg Kroah-Hartman
2019-04-24T18:10:47Z

[ Upstream commit 2803cf4379ed252894f046cb8812a48db35294e3 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/9p/vfs_dir.c | 8 +++-----
net/9p/protocol.c | 3 ++-
2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/fs/9p/vfs_dir.c b/fs/9p/vfs_dir.c
index cfe4cf6486af..fa7d1c3536e6 100644
--- a/fs/9p/vfs_dir.c
+++ b/fs/9p/vfs_dir.c
@@ -104,7 +104,6 @@ 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;

p9_debug(P9_DEBUG_VFS, "name %pD\n", file);
@@ -129,11 +128,10 @@ 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));
@@ -141,8 +139,8 @@ 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 bceb6999614f..66613837b287 100644
--- a/net/9p/protocol.c
+++ b/net/9p/protocol.c
@@ -578,9 +578,10 @@ 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);

--
2.19.1