@@ -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;
}
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 <groug@kaod.org> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> --- hw/9pfs/9p-local.c | 26 +++++++++++++++++--------- 1 file changed, 17 insertions(+), 9 deletions(-)