9pfs: local: utimensat: don't follow symlinks
The local_utimensat() callback is vulnerable to symlink attacks because it
calls qemu_utimens()->utimensat(AT_SYMLINK_NOFOLLOW) which follows symbolic
links in all path elements but the rightmost one or qemu_utimens()->utimes()
which follows symbolic links for all path elements.
This patch converts local_utimensat() to rely on opendir_nofollow() and
utimensat(AT_SYMLINK_NOFOLLOW) directly instead of using qemu_utimens().
It is hence assumed that the OS supports utimensat(), i.e. has glibc 2.6
or higher and linux 2.6.22 or higher, which seems reasonable nowadays.
This partly fixes CVE-2016-9602.
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit a33eda0dd9
)
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
stable-2.8
parent
4286f58bfc
commit
91225c670a
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@ -960,13 +960,20 @@ static int local_chown(FsContext *fs_ctx, V9fsPath *fs_path, FsCred *credp)
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static int local_utimensat(FsContext *s, V9fsPath *fs_path,
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const struct timespec *buf)
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{
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char *buffer;
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int ret;
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char *path = fs_path->data;
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char *dirpath = g_path_get_dirname(fs_path->data);
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char *name = g_path_get_basename(fs_path->data);
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int dirfd, ret = -1;
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buffer = rpath(s, path);
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ret = qemu_utimens(buffer, buf);
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g_free(buffer);
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dirfd = local_opendir_nofollow(s, dirpath);
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if (dirfd == -1) {
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goto out;
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}
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ret = utimensat(dirfd, name, buf, AT_SYMLINK_NOFOLLOW);
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close_preserve_errno(dirfd);
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out:
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g_free(dirpath);
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g_free(name);
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return ret;
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}
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