From: Greg Kurz <groug@kaod.org>
Date: Mon, 6 Mar 2017 16:34:01 +0000 (+0100)
Subject: 9pfs: fix vulnerability in openat_dir() and local_unlinkat_common()
X-Git-Tag: v2.9.0-rc0~22^2
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=b003fc0d8aa5e7060dbf7e5862b8013c73857c7f;p=users%2Fdwmw2%2Fqemu.git

9pfs: fix vulnerability in openat_dir() and local_unlinkat_common()

We should pass O_NOFOLLOW otherwise openat() will follow symlinks and make
QEMU vulnerable.

While here, we also fix local_unlinkat_common() to use openat_dir() for
the same reasons (it was a leftover in the original patchset actually).

This fixes CVE-2016-9602.

Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
---

diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
index 0ca4c94ee4..45e9a1f9b0 100644
--- a/hw/9pfs/9p-local.c
+++ b/hw/9pfs/9p-local.c
@@ -960,7 +960,7 @@ static int local_unlinkat_common(FsContext *ctx, int dirfd, const char *name,
         if (flags == AT_REMOVEDIR) {
             int fd;
 
-            fd = openat(dirfd, name, O_RDONLY | O_DIRECTORY | O_PATH);
+            fd = openat_dir(dirfd, name);
             if (fd == -1) {
                 goto err_out;
             }
diff --git a/hw/9pfs/9p-util.h b/hw/9pfs/9p-util.h
index cb7b2072d3..517027c520 100644
--- a/hw/9pfs/9p-util.h
+++ b/hw/9pfs/9p-util.h
@@ -27,7 +27,8 @@ static inline int openat_dir(int dirfd, const char *name)
 #else
 #define OPENAT_DIR_O_PATH 0
 #endif
-    return openat(dirfd, name, O_DIRECTORY | O_RDONLY | OPENAT_DIR_O_PATH);
+    return openat(dirfd, name,
+                  O_DIRECTORY | O_RDONLY | O_NOFOLLOW | OPENAT_DIR_O_PATH);
 }
 
 static inline int openat_file(int dirfd, const char *name, int flags,