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SUSE:SLE-12-SP5:GA
qemu.29142
0167-9pfs-local-lsetxattr-don-t-follow-s.patch
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File 0167-9pfs-local-lsetxattr-don-t-follow-s.patch of Package qemu.29142
From: Greg Kurz <groug@kaod.org> Date: Sun, 26 Feb 2017 23:42:43 +0100 Subject: 9pfs: local: lsetxattr: don't follow symlinks The local_lsetxattr() callback is vulnerable to symlink attacks because it calls lsetxattr() which follows symbolic links in all path elements but the rightmost one. This patch introduces a helper to emulate the non-existing fsetxattrat() function: it is implemented with /proc/self/fd which provides a trusted path that can be safely passed to lsetxattr(). local_lsetxattr() 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 3e36aba757f76673007a80b3cd56a4062c2e3462) [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 | 18 ++++-------------- hw/9pfs/9p-util.h | 2 ++ hw/9pfs/9p-xattr-user.c | 8 +------- hw/9pfs/9p-xattr.c | 39 +++++++++++++++++++++++++++++++++------ hw/9pfs/9p-xattr.h | 3 +++ 5 files changed, 43 insertions(+), 27 deletions(-) diff --git a/hw/9pfs/9p-posix-acl.c b/hw/9pfs/9p-posix-acl.c index 9435e27a368c5d09769bc30c0aff..0154e2a7605fbf6f5487a4d66e22 100644 --- a/hw/9pfs/9p-posix-acl.c +++ b/hw/9pfs/9p-posix-acl.c @@ -50,13 +50,8 @@ static ssize_t mp_pacl_listxattr(FsContext *ctx, const char *path, static int mp_pacl_setxattr(FsContext *ctx, const char *path, const char *name, void *value, size_t size, int flags) { - char *buffer; - int ret; - - buffer = rpath(ctx, path); - ret = lsetxattr(buffer, MAP_ACL_ACCESS, value, size, flags); - g_free(buffer); - return ret; + return local_setxattr_nofollow(ctx, path, MAP_ACL_ACCESS, value, size, + flags); } static int mp_pacl_removexattr(FsContext *ctx, @@ -108,13 +103,8 @@ static ssize_t mp_dacl_listxattr(FsContext *ctx, const char *path, static int mp_dacl_setxattr(FsContext *ctx, const char *path, const char *name, void *value, size_t size, int flags) { - char *buffer; - int ret; - - buffer = rpath(ctx, path); - ret = lsetxattr(buffer, MAP_ACL_DEFAULT, value, size, flags); - g_free(buffer); - return ret; + return local_setxattr_nofollow(ctx, path, MAP_ACL_DEFAULT, value, size, + flags); } static int mp_dacl_removexattr(FsContext *ctx, diff --git a/hw/9pfs/9p-util.h b/hw/9pfs/9p-util.h index 676641f7c0e0b09d952bb6cdbd3d..091f3ce88e15edb9c323fa903ba0 100644 --- a/hw/9pfs/9p-util.h +++ b/hw/9pfs/9p-util.h @@ -48,5 +48,7 @@ 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); +int fsetxattrat_nofollow(int dirfd, const char *path, const char *name, + void *value, size_t size, int flags); #endif diff --git a/hw/9pfs/9p-xattr-user.c b/hw/9pfs/9p-xattr-user.c index 4071fbc4c08699e650b7be7b0473..1840a5db66f3f92b9ac8b36ce05b 100644 --- a/hw/9pfs/9p-xattr-user.c +++ b/hw/9pfs/9p-xattr-user.c @@ -67,9 +67,6 @@ static ssize_t mp_user_listxattr(FsContext *ctx, const char *path, static int mp_user_setxattr(FsContext *ctx, const char *path, const char *name, void *value, size_t size, int flags) { - char *buffer; - int ret; - if (strncmp(name, "user.virtfs.", 12) == 0) { /* * Don't allow fetch of user.virtfs namesapce @@ -78,10 +75,7 @@ static int mp_user_setxattr(FsContext *ctx, const char *path, const char *name, errno = EACCES; return -1; } - buffer = rpath(ctx, path); - ret = lsetxattr(buffer, name, value, size, flags); - g_free(buffer); - return ret; + return local_setxattr_nofollow(ctx, path, name, value, size, flags); } static int mp_user_removexattr(FsContext *ctx, diff --git a/hw/9pfs/9p-xattr.c b/hw/9pfs/9p-xattr.c index 54193c630c9d0673ad3399db37d2..a0167dd4d898119a5937c0104da4 100644 --- a/hw/9pfs/9p-xattr.c +++ b/hw/9pfs/9p-xattr.c @@ -195,18 +195,45 @@ ssize_t pt_getxattr(FsContext *ctx, const char *path, const char *name, 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) +int fsetxattrat_nofollow(int dirfd, const char *filename, const char *name, + void *value, size_t size, int flags) { - char *buffer; + char *proc_path = g_strdup_printf("/proc/self/fd/%d/%s", dirfd, filename); int ret; - buffer = rpath(ctx, path); - ret = lsetxattr(buffer, name, value, size, flags); - g_free(buffer); + ret = lsetxattr(proc_path, name, value, size, flags); + g_free(proc_path); + return ret; +} + +ssize_t local_setxattr_nofollow(FsContext *ctx, const char *path, + const char *name, void *value, size_t size, + int flags) +{ + 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; + } + + ret = fsetxattrat_nofollow(dirfd, filename, name, value, size, flags); + close_preserve_errno(dirfd); +out: + g_free(dirpath); + g_free(filename); return ret; } +int pt_setxattr(FsContext *ctx, const char *path, const char *name, void *value, + size_t size, int flags) +{ + return local_setxattr_nofollow(ctx, path, name, value, size, flags); +} + int pt_removexattr(FsContext *ctx, const char *path, const char *name) { char *buffer; diff --git a/hw/9pfs/9p-xattr.h b/hw/9pfs/9p-xattr.h index d9d7ce15b24799145a797ee5b5dc..e47f729ec6732fcffe346232de14 100644 --- a/hw/9pfs/9p-xattr.h +++ b/hw/9pfs/9p-xattr.h @@ -30,6 +30,9 @@ typedef struct xattr_operations ssize_t local_getxattr_nofollow(FsContext *ctx, const char *path, const char *name, void *value, size_t size); +ssize_t local_setxattr_nofollow(FsContext *ctx, const char *path, + const char *name, void *value, size_t size, + int flags); extern XattrOperations mapped_user_xattr; extern XattrOperations passthrough_user_xattr;
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