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[Qemu-devel] [PATCH 16/81] 9pfs: local: readlink: don't follow symlinks
From: |
Michael Roth |
Subject: |
[Qemu-devel] [PATCH 16/81] 9pfs: local: readlink: don't follow symlinks |
Date: |
Mon, 20 Mar 2017 18:07:40 -0500 |
From: Greg Kurz <address@hidden>
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>
(cherry picked from commit bec1e9546e03b9e7f5152cf3e8c95cf8acff5e12)
Signed-off-by: Greg Kurz <address@hidden>
Signed-off-by: Michael Roth <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 5e206e1..c290b6c 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] [PATCH 00/81] Patch Round-up for stable 2.8.1, freeze on 2017-03-27, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 10/81] 9pfs: local: lremovexattr: don't follow symlinks, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 11/81] 9pfs: local: unlinkat: don't follow symlinks, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 09/81] 9pfs: local: lsetxattr: don't follow symlinks, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 13/81] 9pfs: local: utimensat: don't follow symlinks, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 14/81] 9pfs: local: statfs: don't follow symlinks, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 15/81] 9pfs: local: truncate: don't follow symlinks, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 12/81] 9pfs: local: remove: don't follow symlinks, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 19/81] 9pfs: local: rename: use renameat, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 17/81] 9pfs: local: lstat: don't follow symlinks, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 16/81] 9pfs: local: readlink: don't follow symlinks,
Michael Roth <=
- [Qemu-devel] [PATCH 21/81] 9pfs: local: link: don't follow symlinks, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 18/81] 9pfs: local: renameat: don't follow symlinks, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 29/81] 9pfs: fix bogus fd check in local_remove(), Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 25/81] 9pfs: local: mknod: don't follow symlinks, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 01/81] 9pfs: local: move xattr security ops to 9p-xattr.c, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 20/81] 9pfs: local: improve error handling in link op, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 23/81] 9pfs: local: chown: don't follow symlinks, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 22/81] 9pfs: local: chmod: don't follow symlinks, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 28/81] 9pfs: local: drop unused code, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 27/81] 9pfs: local: open2: don't follow symlinks, Michael Roth, 2017/03/20