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SUSE:SLE-12-SP2:GA
qemu-linux-user.6353
0220-9pfs-local-lgetxattr-don-t-follow-s.patch
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File 0220-9pfs-local-lgetxattr-don-t-follow-s.patch of Package qemu-linux-user.6353
From bfa26c7e355ee282a4ba13de891bc74dd36a96b3 Mon Sep 17 00:00:00 2001 From: Greg Kurz <groug@kaod.org> Date: Sun, 26 Feb 2017 23:42:26 +0100 Subject: [PATCH] 9pfs: local: lgetxattr: don't follow symlinks The local_lgetxattr() callback is vulnerable to symlink attacks because it calls lgetxattr() which follows symbolic links in all path elements but the rightmost one. This patch introduces a helper to emulate the non-existing fgetxattrat() function: it is implemented with /proc/self/fd which provides a trusted path that can be safely passed to lgetxattr(). local_lgetxattr() is converted to use this helper and opendir_nofollow(). 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 56ad3e54dad6cdcee8668d170df161d89581846f) [BR: Fix and/or infrastructure for BSC#1020427 CVE-2016-9602] Signed-off-by: Bruce Rogers <brogers@suse.com> --- hw/9pfs/9p-posix-acl.c | 16 ++-------------- hw/9pfs/9p-util.c | 12 ++++++++++++ hw/9pfs/9p-util.h | 2 ++ hw/9pfs/9p-xattr-user.c | 8 +------- hw/9pfs/9p-xattr.c | 31 ++++++++++++++++++++++++------- hw/9pfs/9p-xattr.h | 2 ++ 6 files changed, 43 insertions(+), 28 deletions(-) diff --git a/hw/9pfs/9p-posix-acl.c b/hw/9pfs/9p-posix-acl.c index 8df822833c..d7ebf641f8 100644 --- a/hw/9pfs/9p-posix-acl.c +++ b/hw/9pfs/9p-posix-acl.c @@ -25,13 +25,7 @@ static ssize_t mp_pacl_getxattr(FsContext *ctx, const char *path, const char *name, void *value, size_t size) { - char *buffer; - ssize_t ret; - - buffer = rpath(ctx, path); - ret = lgetxattr(buffer, MAP_ACL_ACCESS, value, size); - g_free(buffer); - return ret; + return local_getxattr_nofollow(ctx, path, MAP_ACL_ACCESS, value, size); } static ssize_t mp_pacl_listxattr(FsContext *ctx, const char *path, @@ -89,13 +83,7 @@ static int mp_pacl_removexattr(FsContext *ctx, static ssize_t mp_dacl_getxattr(FsContext *ctx, const char *path, const char *name, void *value, size_t size) { - char *buffer; - ssize_t ret; - - buffer = rpath(ctx, path); - ret = lgetxattr(buffer, MAP_ACL_DEFAULT, value, size); - g_free(buffer); - return ret; + return local_getxattr_nofollow(ctx, path, MAP_ACL_DEFAULT, value, size); } static ssize_t mp_dacl_listxattr(FsContext *ctx, const char *path, diff --git a/hw/9pfs/9p-util.c b/hw/9pfs/9p-util.c index f8d47aa271..a8db449592 100644 --- a/hw/9pfs/9p-util.c +++ b/hw/9pfs/9p-util.c @@ -19,6 +19,7 @@ #include <assert.h> #include "glib-compat.h" #include "qemu/osdep.h" +#include "qemu/xattr.h" #include "9p-util.h" int relative_openat_nofollow(int dirfd, const char *path, int flags, @@ -63,3 +64,14 @@ int relative_openat_nofollow(int dirfd, const char *path, int flags, return fd; } + +ssize_t fgetxattrat_nofollow(int dirfd, const char *filename, const char *name, + void *value, size_t size) +{ + char *proc_path = g_strdup_printf("/proc/self/fd/%d/%s", dirfd, filename); + int ret; + + ret = lgetxattr(proc_path, name, value, size); + g_free(proc_path); + return ret; +} diff --git a/hw/9pfs/9p-util.h b/hw/9pfs/9p-util.h index e80b5a551d..676641f7c0 100644 --- a/hw/9pfs/9p-util.h +++ b/hw/9pfs/9p-util.h @@ -46,5 +46,7 @@ static inline int openat_file(int dirfd, const char *name, int flags, int relative_openat_nofollow(int dirfd, const char *path, int flags, mode_t mode); +ssize_t fgetxattrat_nofollow(int dirfd, const char *path, const char *name, + void *value, size_t size); #endif diff --git a/hw/9pfs/9p-xattr-user.c b/hw/9pfs/9p-xattr-user.c index c490ec3bf0..6e9d9da974 100644 --- a/hw/9pfs/9p-xattr-user.c +++ b/hw/9pfs/9p-xattr-user.c @@ -20,9 +20,6 @@ static ssize_t mp_user_getxattr(FsContext *ctx, const char *path, const char *name, void *value, size_t size) { - char *buffer; - ssize_t ret; - if (strncmp(name, "user.virtfs.", 12) == 0) { /* * Don't allow fetch of user.virtfs namesapce @@ -31,10 +28,7 @@ static ssize_t mp_user_getxattr(FsContext *ctx, const char *path, errno = ENOATTR; return -1; } - buffer = rpath(ctx, path); - ret = lgetxattr(buffer, name, value, size); - g_free(buffer); - return ret; + return local_getxattr_nofollow(ctx, path, name, value, size); } static ssize_t mp_user_listxattr(FsContext *ctx, const char *path, diff --git a/hw/9pfs/9p-xattr.c b/hw/9pfs/9p-xattr.c index f593e1aca5..cab0ee0bc3 100644 --- a/hw/9pfs/9p-xattr.c +++ b/hw/9pfs/9p-xattr.c @@ -14,6 +14,8 @@ #include "9p.h" #include "fsdev/file-op-9p.h" #include "9p-xattr.h" +#include "9p-util.h" +#include "9p-local.h" static XattrOperations *get_xattr_operations(XattrOperations **h, @@ -142,18 +144,33 @@ int v9fs_remove_xattr(FsContext *ctx, } -ssize_t pt_getxattr(FsContext *ctx, const char *path, const char *name, - void *value, size_t size) +ssize_t local_getxattr_nofollow(FsContext *ctx, const char *path, + const char *name, void *value, size_t size) { - char *buffer; - ssize_t ret; + char *dirpath = g_path_get_dirname(path); + char *filename = g_path_get_basename(path); + int dirfd; + ssize_t ret = -1; + + dirfd = local_opendir_nofollow(ctx, dirpath); + if (dirfd == -1) { + goto out; + } - buffer = rpath(ctx, path); - ret = lgetxattr(buffer, name, value, size); - g_free(buffer); + ret = fgetxattrat_nofollow(dirfd, filename, name, value, size); + close_preserve_errno(dirfd); +out: + g_free(dirpath); + g_free(filename); return ret; } +ssize_t pt_getxattr(FsContext *ctx, const char *path, const char *name, + void *value, size_t size) +{ + return local_getxattr_nofollow(ctx, path, name, value, size); +} + int pt_setxattr(FsContext *ctx, const char *path, const char *name, void *value, size_t size, int flags) { diff --git a/hw/9pfs/9p-xattr.h b/hw/9pfs/9p-xattr.h index e3ee5fa91e..d9d7ce15b2 100644 --- a/hw/9pfs/9p-xattr.h +++ b/hw/9pfs/9p-xattr.h @@ -28,6 +28,8 @@ typedef struct xattr_operations const char *path, const char *name); } XattrOperations; +ssize_t local_getxattr_nofollow(FsContext *ctx, const char *path, + const char *name, void *value, size_t size); extern XattrOperations mapped_user_xattr; extern XattrOperations passthrough_user_xattr;
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