From 4bc799dcb67066e0531004d5bdbe755bb02b5488 Mon Sep 17 00:00:00 2001 From: Sami Tolvanen Date: Mon, 15 Jun 2020 11:12:32 -0700 Subject: [PATCH 1/2] security: fix the key_permission LSM hook function type Commit 8c0637e950d6 ("keys: Make the KEY_NEED_* perms an enum rather than a mask") changed the type of the key_permission callback functions, but didn't change the type of the hook, which trips indirect call checking with Control-Flow Integrity (CFI). This change fixes the issue by changing the hook type to match the functions. Fixes: 8c0637e950d6 ("keys: Make the KEY_NEED_* perms an enum rather than a mask") Signed-off-by: Sami Tolvanen Acked-by: Kees Cook Signed-off-by: James Morris --- include/linux/lsm_hook_defs.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h index 6791813cd439..24f6683f1cfc 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -360,7 +360,7 @@ LSM_HOOK(int, 0, key_alloc, struct key *key, const struct cred *cred, unsigned long flags) LSM_HOOK(void, LSM_RET_VOID, key_free, struct key *key) LSM_HOOK(int, 0, key_permission, key_ref_t key_ref, const struct cred *cred, - unsigned perm) + enum key_need_perm need_perm) LSM_HOOK(int, 0, key_getsecurity, struct key *key, char **_buffer) #endif /* CONFIG_KEYS */ From 23e390cdbe6f85827a43d38f9288dcd3066fa376 Mon Sep 17 00:00:00 2001 From: KP Singh Date: Mon, 22 Jun 2020 00:21:35 +0200 Subject: [PATCH 2/2] security: Fix hook iteration and default value for inode_copy_up_xattr inode_copy_up_xattr returns 0 to indicate the acceptance of the xattr and 1 to reject it. If the LSM does not know about the xattr, it's expected to return -EOPNOTSUPP, which is the correct default value for this hook. BPF LSM, currently, uses 0 as the default value and thereby falsely allows all overlay fs xattributes to be copied up. The iteration logic is also updated from the "bail-on-fail" call_int_hook to continue on the non-decisive -EOPNOTSUPP and bail out on other values. Fixes: 98e828a0650f ("security: Refactor declaration of LSM hooks") Signed-off-by: KP Singh Signed-off-by: James Morris --- include/linux/lsm_hook_defs.h | 2 +- security/security.c | 17 ++++++++++++++++- 2 files changed, 17 insertions(+), 2 deletions(-) diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h index 24f6683f1cfc..af998f93d256 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -150,7 +150,7 @@ LSM_HOOK(int, 0, inode_listsecurity, struct inode *inode, char *buffer, size_t buffer_size) LSM_HOOK(void, LSM_RET_VOID, inode_getsecid, struct inode *inode, u32 *secid) LSM_HOOK(int, 0, inode_copy_up, struct dentry *src, struct cred **new) -LSM_HOOK(int, 0, inode_copy_up_xattr, const char *name) +LSM_HOOK(int, -EOPNOTSUPP, inode_copy_up_xattr, const char *name) LSM_HOOK(int, 0, kernfs_init_security, struct kernfs_node *kn_dir, struct kernfs_node *kn) LSM_HOOK(int, 0, file_permission, struct file *file, int mask) diff --git a/security/security.c b/security/security.c index 0ce3e73edd42..70a7ad357bc6 100644 --- a/security/security.c +++ b/security/security.c @@ -1414,7 +1414,22 @@ EXPORT_SYMBOL(security_inode_copy_up); int security_inode_copy_up_xattr(const char *name) { - return call_int_hook(inode_copy_up_xattr, -EOPNOTSUPP, name); + struct security_hook_list *hp; + int rc; + + /* + * The implementation can return 0 (accept the xattr), 1 (discard the + * xattr), -EOPNOTSUPP if it does not know anything about the xattr or + * any other error code incase of an error. + */ + hlist_for_each_entry(hp, + &security_hook_heads.inode_copy_up_xattr, list) { + rc = hp->hook.inode_copy_up_xattr(name); + if (rc != LSM_RET_DEFAULT(inode_copy_up_xattr)) + return rc; + } + + return LSM_RET_DEFAULT(inode_copy_up_xattr); } EXPORT_SYMBOL(security_inode_copy_up_xattr);