diff options
author | David Windsor <dave@nullcore.net> | 2017-06-11 04:50:30 +0200 |
---|---|---|
committer | Kees Cook <keescook@chromium.org> | 2018-01-15 21:07:50 +0100 |
commit | 6a9b88204cb00da2140afda27848b5d17a7402a3 (patch) | |
tree | dc14b149527a358af4e3017da1e014f0c7d4ff7b /fs/dcache.c | |
parent | dcache: Define usercopy region in dentry_cache slab cache (diff) | |
download | linux-6a9b88204cb00da2140afda27848b5d17a7402a3.tar.xz linux-6a9b88204cb00da2140afda27848b5d17a7402a3.zip |
vfs: Define usercopy region in names_cache slab caches
VFS pathnames are stored in the names_cache slab cache, either inline
or across an entire allocation entry (when approaching PATH_MAX). These
are copied to/from userspace, so they must be entirely whitelisted.
cache object allocation:
include/linux/fs.h:
#define __getname() kmem_cache_alloc(names_cachep, GFP_KERNEL)
example usage trace:
strncpy_from_user+0x4d/0x170
getname_flags+0x6f/0x1f0
user_path_at_empty+0x23/0x40
do_mount+0x69/0xda0
SyS_mount+0x83/0xd0
fs/namei.c:
getname_flags(...):
...
result = __getname();
...
kname = (char *)result->iname;
result->name = kname;
len = strncpy_from_user(kname, filename, EMBEDDED_NAME_MAX);
...
if (unlikely(len == EMBEDDED_NAME_MAX)) {
const size_t size = offsetof(struct filename, iname[1]);
kname = (char *)result;
result = kzalloc(size, GFP_KERNEL);
...
result->name = kname;
len = strncpy_from_user(kname, filename, PATH_MAX);
In support of usercopy hardening, this patch defines the entire cache
object in the names_cache slab cache as whitelisted, since it may entirely
hold name strings to be copied to/from userspace.
This patch is verbatim from Brad Spengler/PaX Team's PAX_USERCOPY
whitelisting code in the last public patch of grsecurity/PaX based on my
understanding of the code. Changes or omissions from the original code are
mine and don't reflect the original grsecurity/PaX code.
Signed-off-by: David Windsor <dave@nullcore.net>
[kees: adjust commit log, add usage trace]
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Diffstat (limited to 'fs/dcache.c')
-rw-r--r-- | fs/dcache.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/fs/dcache.c b/fs/dcache.c index 92ad7a2168e1..9d7ee2de682c 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -3640,8 +3640,8 @@ void __init vfs_caches_init_early(void) void __init vfs_caches_init(void) { - names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0, - SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); + names_cachep = kmem_cache_create_usercopy("names_cache", PATH_MAX, 0, + SLAB_HWCACHE_ALIGN|SLAB_PANIC, 0, PATH_MAX, NULL); dcache_init(); inode_init(); |