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[Qemu-devel] [PULL 16/28] 9pfs: local: readlink: don't follow symlinks
From: |
Greg Kurz |
Subject: |
[Qemu-devel] [PULL 16/28] 9pfs: local: readlink: don't follow symlinks |
Date: |
Tue, 28 Feb 2017 11:30:28 +0100 |
The local_readlink() callback is vulnerable to symlink attacks because it
calls:
(1) open(O_NOFOLLOW) which follows symbolic links for all path elements but
the rightmost one
(2) readlink() which follows symbolic links for all path elements but the
rightmost one
This patch converts local_readlink() to rely on open_nofollow() to fix (1)
and opendir_nofollow(), readlinkat() to fix (2).
This partly fixes CVE-2016-9602.
Signed-off-by: Greg Kurz <address@hidden>
Reviewed-by: Stefan Hajnoczi <address@hidden>
---
hw/9pfs/9p-local.c | 26 +++++++++++++++++---------
1 file changed, 17 insertions(+), 9 deletions(-)
diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
index 1a3dfd774012..e373cca3b78d 100644
--- a/hw/9pfs/9p-local.c
+++ b/hw/9pfs/9p-local.c
@@ -340,27 +340,35 @@ static ssize_t local_readlink(FsContext *fs_ctx, V9fsPath
*fs_path,
char *buf, size_t bufsz)
{
ssize_t tsize = -1;
- char *buffer;
- char *path = fs_path->data;
if ((fs_ctx->export_flags & V9FS_SM_MAPPED) ||
(fs_ctx->export_flags & V9FS_SM_MAPPED_FILE)) {
int fd;
- buffer = rpath(fs_ctx, path);
- fd = open(buffer, O_RDONLY | O_NOFOLLOW);
- g_free(buffer);
+
+ fd = local_open_nofollow(fs_ctx, fs_path->data, O_RDONLY, 0);
if (fd == -1) {
return -1;
}
do {
tsize = read(fd, (void *)buf, bufsz);
} while (tsize == -1 && errno == EINTR);
- close(fd);
+ close_preserve_errno(fd);
} else if ((fs_ctx->export_flags & V9FS_SM_PASSTHROUGH) ||
(fs_ctx->export_flags & V9FS_SM_NONE)) {
- buffer = rpath(fs_ctx, path);
- tsize = readlink(buffer, buf, bufsz);
- g_free(buffer);
+ char *dirpath = g_path_get_dirname(fs_path->data);
+ char *name = g_path_get_basename(fs_path->data);
+ int dirfd;
+
+ dirfd = local_opendir_nofollow(fs_ctx, dirpath);
+ if (dirfd == -1) {
+ goto out;
+ }
+
+ tsize = readlinkat(dirfd, name, buf, bufsz);
+ close_preserve_errno(dirfd);
+ out:
+ g_free(name);
+ g_free(dirpath);
}
return tsize;
}
--
2.7.4
- [Qemu-devel] [PULL 05/28] 9pfs: local: keep a file descriptor on the shared folder, (continued)
- [Qemu-devel] [PULL 05/28] 9pfs: local: keep a file descriptor on the shared folder, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 06/28] 9pfs: local: open/opendir: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 04/28] 9pfs: introduce relative_openat_nofollow() helper, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 09/28] 9pfs: local: lsetxattr: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 07/28] 9pfs: local: lgetxattr: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 08/28] 9pfs: local: llistxattr: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 12/28] 9pfs: local: remove: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 13/28] 9pfs: local: utimensat: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 11/28] 9pfs: local: unlinkat: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 14/28] 9pfs: local: statfs: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 16/28] 9pfs: local: readlink: don't follow symlinks,
Greg Kurz <=
- [Qemu-devel] [PULL 10/28] 9pfs: local: lremovexattr: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 15/28] 9pfs: local: truncate: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 17/28] 9pfs: local: lstat: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 19/28] 9pfs: local: rename: use renameat, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 18/28] 9pfs: local: renameat: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 20/28] 9pfs: local: improve error handling in link op, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 25/28] 9pfs: local: mknod: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 22/28] 9pfs: local: chmod: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 23/28] 9pfs: local: chown: don't follow symlinks, Greg Kurz, 2017/02/28
- [Qemu-devel] [PULL 24/28] 9pfs: local: symlink: don't follow symlinks, Greg Kurz, 2017/02/28