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[Qemu-devel] [PATCH 15/29] 9pfs: local: statfs: don't follow symlinks


From: Greg Kurz
Subject: [Qemu-devel] [PATCH 15/29] 9pfs: local: statfs: don't follow symlinks
Date: Mon, 20 Feb 2017 15:41:16 +0100
User-agent: StGit/0.17.1-20-gc0b1b-dirty

The local_statfs() callback is vulnerable to symlink attacks because it
calls statfs() which follows symbolic links in all path elements.

This patch converts local_statfs() to rely on open_nofollow() and fstatfs()
instead.

This partly fixes CVE-2016-9602.

Signed-off-by: Greg Kurz <address@hidden>
---
 hw/9pfs/9p-local.c |   10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
index 7f3d9dd9a499..ebc12f3c0691 100644
--- a/hw/9pfs/9p-local.c
+++ b/hw/9pfs/9p-local.c
@@ -1072,13 +1072,11 @@ static int local_fsync(FsContext *ctx, int fid_type,
 
 static int local_statfs(FsContext *s, V9fsPath *fs_path, struct statfs *stbuf)
 {
-    char *buffer;
-    int ret;
-    char *path = fs_path->data;
+    int fd, ret;
 
-    buffer = rpath(s, path);
-    ret = statfs(buffer, stbuf);
-    g_free(buffer);
+    fd = local_open_nofollow(s, fs_path->data, O_RDONLY, 0);
+    ret = fstatfs(fd, stbuf);
+    close_preserve_errno(fd);
     return ret;
 }
 




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