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authorDavid Windsor <dave@nullcore.net>2017-06-11 04:50:30 +0200
committerKees Cook <keescook@chromium.org>2018-01-15 21:07:50 +0100
commit6a9b88204cb00da2140afda27848b5d17a7402a3 (patch)
treedc14b149527a358af4e3017da1e014f0c7d4ff7b /fs/dcache.c
parentdcache: Define usercopy region in dentry_cache slab cache (diff)
downloadlinux-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.c4
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();