9p: p9dirent_read: check network-provided name length

[ Upstream commit ef5305f1f72eb1cfcda25c382bb0368509c0385b ]

strcpy to dirent->d_name could overflow the buffer, use strscpy to check
the provided string length and error out if the size was too big.

While we are here, make the function return an error when the pdu
parsing failed, instead of returning the pdu offset as if it had been a
success...

Link: http://lkml.kernel.org/r/1536339057-21974-4-git-send-email-asmadeus@codewreck.org
Addresses-Coverity-ID: 139133 ("Copy into fixed size buffer")
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/9p/protocol.c b/net/9p/protocol.c
index 766d1ef4640a316022f91bcc3e4e9a495e4a7e56..1885403c9a3ecc449ae08cd628e59cc06b834409 100644 (file)
--- a/net/9p/protocol.c
+++ b/net/9p/protocol.c
@@ -622,13 +622,19 @@ int p9dirent_read(struct p9_client *clnt, char *buf, int len,
        if (ret) {
                p9_debug(P9_DEBUG_9P, "<<< p9dirent_read failed: %d\n", ret);
                trace_9p_protocol_dump(clnt, &fake_pdu);
-               goto out;
+               return ret;
        }
 
-       strcpy(dirent->d_name, nameptr);
+       ret = strscpy(dirent->d_name, nameptr, sizeof(dirent->d_name));
+       if (ret < 0) {
+               p9_debug(P9_DEBUG_ERROR,
+                        "On the wire dirent name too long: %s\n",
+                        nameptr);
+               kfree(nameptr);
+               return ret;
+       }
        kfree(nameptr);
 
-out:
        return fake_pdu.offset;
 }
 EXPORT_SYMBOL(p9dirent_read);