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author | Greg Kurz <groug@kaod.org> | 2017-02-26 23:43:17 +0100 |
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committer | Greg Kurz <groug@kaod.org> | 2017-02-28 11:21:15 +0100 |
commit | a33eda0dd99e00faa3bacae43d19490bb9500e07 (patch) | |
tree | 82dddab6b93ce1d9fa0743055c16aa8a211392f4 /hw/9pfs | |
parent | a0e640a87210b1e986bcd4e7f7de03beb3db0a4a (diff) | |
download | qemu-a33eda0dd99e00faa3bacae43d19490bb9500e07.zip qemu-a33eda0dd99e00faa3bacae43d19490bb9500e07.tar.gz qemu-a33eda0dd99e00faa3bacae43d19490bb9500e07.tar.bz2 |
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>
Diffstat (limited to 'hw/9pfs')
-rw-r--r-- | hw/9pfs/9p-local.c | 19 |
1 files changed, 13 insertions, 6 deletions
diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c index 8fb79e4..a6dd77d 100644 --- a/hw/9pfs/9p-local.c +++ b/hw/9pfs/9p-local.c @@ -959,13 +959,20 @@ static int local_chown(FsContext *fs_ctx, V9fsPath *fs_path, FsCred *credp) static int local_utimensat(FsContext *s, V9fsPath *fs_path, const struct timespec *buf) { - char *buffer; - int ret; - char *path = fs_path->data; + char *dirpath = g_path_get_dirname(fs_path->data); + char *name = g_path_get_basename(fs_path->data); + int dirfd, ret = -1; - buffer = rpath(s, path); - ret = qemu_utimens(buffer, buf); - g_free(buffer); + dirfd = local_opendir_nofollow(s, dirpath); + if (dirfd == -1) { + goto out; + } + + ret = utimensat(dirfd, name, buf, AT_SYMLINK_NOFOLLOW); + close_preserve_errno(dirfd); +out: + g_free(dirpath); + g_free(name); return ret; } |