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[Qemu-devel] [PATCH 08/81] 9pfs: local: llistxattr: don't follow symlink
From: |
Michael Roth |
Subject: |
[Qemu-devel] [PATCH 08/81] 9pfs: local: llistxattr: don't follow symlinks |
Date: |
Mon, 20 Mar 2017 18:07:32 -0500 |
From: Greg Kurz <address@hidden>
The local_llistxattr() callback is vulnerable to symlink attacks because
it calls llistxattr() which follows symbolic links in all path elements but
the rightmost one.
This patch introduces a helper to emulate the non-existing flistxattrat()
function: it is implemented with /proc/self/fd which provides a trusted
path that can be safely passed to llistxattr().
local_llistxattr() is converted to use this helper and opendir_nofollow().
This partly fixes CVE-2016-9602.
Signed-off-by: Greg Kurz <address@hidden>
Reviewed-by: Stefan Hajnoczi <address@hidden>
(cherry picked from commit 5507904e362df252f6065cb27d1ff98372db6abc)
Signed-off-by: Greg Kurz <address@hidden>
Signed-off-by: Michael Roth <address@hidden>
---
hw/9pfs/9p-xattr.c | 35 +++++++++++++++++++++++++++++------
1 file changed, 29 insertions(+), 6 deletions(-)
diff --git a/hw/9pfs/9p-xattr.c b/hw/9pfs/9p-xattr.c
index aa4391e..54193c6 100644
--- a/hw/9pfs/9p-xattr.c
+++ b/hw/9pfs/9p-xattr.c
@@ -60,6 +60,16 @@ ssize_t pt_listxattr(FsContext *ctx, const char *path,
return name_size;
}
+static ssize_t flistxattrat_nofollow(int dirfd, const char *filename,
+ char *list, size_t size)
+{
+ char *proc_path = g_strdup_printf("/proc/self/fd/%d/%s", dirfd, filename);
+ int ret;
+
+ ret = llistxattr(proc_path, list, size);
+ g_free(proc_path);
+ return ret;
+}
/*
* Get the list and pass to each layer to find out whether
@@ -69,24 +79,37 @@ ssize_t v9fs_list_xattr(FsContext *ctx, const char *path,
void *value, size_t vsize)
{
ssize_t size = 0;
- char *buffer;
void *ovalue = value;
XattrOperations *xops;
char *orig_value, *orig_value_start;
ssize_t xattr_len, parsed_len = 0, attr_len;
+ char *dirpath, *name;
+ int dirfd;
/* Get the actual len */
- buffer = rpath(ctx, path);
- xattr_len = llistxattr(buffer, value, 0);
+ dirpath = g_path_get_dirname(path);
+ dirfd = local_opendir_nofollow(ctx, dirpath);
+ g_free(dirpath);
+ if (dirfd == -1) {
+ return -1;
+ }
+
+ name = g_path_get_basename(path);
+ xattr_len = flistxattrat_nofollow(dirfd, name, value, 0);
if (xattr_len <= 0) {
- g_free(buffer);
+ g_free(name);
+ close_preserve_errno(dirfd);
return xattr_len;
}
/* Now fetch the xattr and find the actual size */
orig_value = g_malloc(xattr_len);
- xattr_len = llistxattr(buffer, orig_value, xattr_len);
- g_free(buffer);
+ xattr_len = flistxattrat_nofollow(dirfd, name, orig_value, xattr_len);
+ g_free(name);
+ close_preserve_errno(dirfd);
+ if (xattr_len < 0) {
+ return -1;
+ }
/* store the orig pointer */
orig_value_start = orig_value;
--
2.7.4
- [Qemu-devel] [PATCH 49/81] char: fix ctrl-a b not working, (continued)
- [Qemu-devel] [PATCH 49/81] char: fix ctrl-a b not working, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 51/81] tcg/aarch64: Fix tcg_out_movi, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 52/81] ui: use evdev keymap when running under wayland, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 56/81] cirrus: fix oob access issue (CVE-2017-2615), Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 70/81] qga: ignore EBUSY when freezing a filesystem, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 75/81] NetRxPkt: Do not try to pull more data than present, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 06/81] 9pfs: local: open/opendir: don't follow symlinks, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 59/81] target/s390x: use "qemu" cpu model in user mode, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 74/81] NetRxPkt: Fix memory corruption on VLAN header stripping, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 69/81] target-i386: correctly propagate retaddr into SVM helpers, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 08/81] 9pfs: local: llistxattr: don't follow symlinks,
Michael Roth <=
- [Qemu-devel] [PATCH 61/81] block/nfs: fix NULL pointer dereference in URI parsing, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 05/81] 9pfs: local: keep a file descriptor on the shared folder, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 64/81] vnc: do not disconnect on EAGAIN, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 63/81] sd: sdhci: check data length during dma_memory_read, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 76/81] NetRxPkt: Account buffer with ETH header in IOV length, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 66/81] block/vmdk: Fix the endian problem of buf_len and lba, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 73/81] eth: Extend vlan stripping functions, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 77/81] e1000e: correctly tear down MSI-X memory regions, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 78/81] scsi: mptsas: fix the wrong reading size in fetch request, Michael Roth, 2017/03/20
- [Qemu-devel] [PATCH 81/81] thread-pool: add missing qemu_bh_cancel in completion function, Michael Roth, 2017/03/20