* [PATCH v2] evm: Correct inode_init_security hooks behaviors
@ 2022-10-21 15:14 Nicolas Bouchinet
2022-10-21 15:42 ` Casey Schaufler
0 siblings, 1 reply; 3+ messages in thread
From: Nicolas Bouchinet @ 2022-10-21 15:14 UTC (permalink / raw)
To: linux-integrity
Cc: philippe.trebuchet, zohar, dmitry.kasatkin, paul, jmorris, serge,
casey, davem, lucien.xin, vgoyal, omosnace, mortonm,
nicolas.bouchinet, mic, cgzones, linux-security-module
From: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr>
Fixes a NULL pointer dereference occurring in the
`evm_protected_xattr_common` function of the EVM LSM. The bug is
triggered if a `inode_init_security` hook returns 0 without initializing
the given `struct xattr` fields (which is the case of BPF) and if no
other LSM overrides thoses fields after. This also leads to memory
leaks.
Adds a `call_int_hook_xattr` macro that fetches and feed the
`new_xattrs` array with every called hook xattr values.
Adds a `evm_init_hmacs` function which init the EVM hmac using every
entry of the array contrary to `evm_init_hmac`.
Fixes the `evm_inode_init_security` function to use `evm_init_hmacs`.
The `MAX_LSM_EVM_XATTR` value has been raised to 5 which gives room for
SMACK, SELinux, Apparmor, BPF and IMA/EVM security attributes.
Changes the default return value of the `inode_init_security` hook
definition to `-EOPNOTSUPP`.
Changes the hook documentation to match the behavior of the LSMs using
it (only xattr->value is initialised with kmalloc and thus is the only
one that should be kfreed by the caller).
Cc: stable@vger.kernel.org
Signed-off-by: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr>
---
Changes since v1:
https://lore.kernel.org/linux-integrity/Y1FTSIo+1x+4X0LS@archlinux/
* The `call_int_hook_xattr` macro has been inlined into the
`security_inode_init_security` hook (as suggested by Paul Moor,
Mickaël Salaün and Casey Schaufler).
* The MAX_LSM_EVM_XATTR value is processed based on compiled LSMs (as
proposed by Casey Schaufler).
* Various typos and cosmetic changes has been fixed (as suggested by
Mickaël Salaün)
* A MAX_LSM_EVM_XATTR test has been wrapped in a WAN_ON_ONCE macro (as
suggested by Mickaël Salaün).
---
include/linux/lsm_hook_defs.h | 2 +-
include/linux/lsm_hooks.h | 4 ++--
security/integrity/evm/evm.h | 2 ++
security/integrity/evm/evm_crypto.c | 22 ++++++++++++++++++++++
security/integrity/evm/evm_main.c | 9 +++++----
security/security.c | 28 +++++++++++++++++++++-------
6 files changed, 53 insertions(+), 14 deletions(-)
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 806448173033..e5dd0c0f6345 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -111,7 +111,7 @@ LSM_HOOK(int, 0, path_notify, const struct path *path, u64 mask,
unsigned int obj_type)
LSM_HOOK(int, 0, inode_alloc_security, struct inode *inode)
LSM_HOOK(void, LSM_RET_VOID, inode_free_security, struct inode *inode)
-LSM_HOOK(int, 0, inode_init_security, struct inode *inode,
+LSM_HOOK(int, -EOPNOTSUPP, inode_init_security, struct inode *inode,
struct inode *dir, const struct qstr *qstr, const char **name,
void **value, size_t *len)
LSM_HOOK(int, 0, inode_init_security_anon, struct inode *inode,
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 84a0d7e02176..95aff9383de1 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -229,8 +229,8 @@
* This hook is called by the fs code as part of the inode creation
* transaction and provides for atomic labeling of the inode, unlike
* the post_create/mkdir/... hooks called by the VFS. The hook function
- * is expected to allocate the name and value via kmalloc, with the caller
- * being responsible for calling kfree after using them.
+ * is expected to allocate the value via kmalloc, with the caller
+ * being responsible for calling kfree after using it.
* If the security module does not use security attributes or does
* not wish to put a security attribute on this particular inode,
* then it should return -EOPNOTSUPP to skip this processing.
diff --git a/security/integrity/evm/evm.h b/security/integrity/evm/evm.h
index f8b8c5004fc7..a2f9886e924d 100644
--- a/security/integrity/evm/evm.h
+++ b/security/integrity/evm/evm.h
@@ -60,6 +60,8 @@ int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name,
struct evm_digest *data);
int evm_init_hmac(struct inode *inode, const struct xattr *xattr,
char *hmac_val);
+int evm_init_hmacs(struct inode *inode, const struct xattr *xattrs,
+ char *hmac_val);
int evm_init_secfs(void);
#endif
diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
index 708de9656bbd..db6868875e09 100644
--- a/security/integrity/evm/evm_crypto.c
+++ b/security/integrity/evm/evm_crypto.c
@@ -385,6 +385,28 @@ int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
return rc;
}
+int evm_protected_xattr(const char *req_xattr_name);
+
+int evm_init_hmacs(struct inode *inode, const struct xattr *lsm_xattrs,
+ char *hmac_val)
+{
+ struct shash_desc *desc;
+
+ desc = init_desc(EVM_XATTR_HMAC, HASH_ALGO_SHA1);
+ if (IS_ERR(desc)) {
+ pr_info("init_desc failed\n");
+ return PTR_ERR(desc);
+ }
+
+ for (int i = 0; lsm_xattrs[i].value != NULL; i++) {
+ if (evm_protected_xattr(lsm_xattrs[i].name))
+ crypto_shash_update(desc, lsm_xattrs[i].value, lsm_xattrs[i].value_len);
+ }
+ hmac_add_misc(desc, inode, EVM_XATTR_HMAC, hmac_val);
+ kfree(desc);
+ return 0;
+}
+
int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattr,
char *hmac_val)
{
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index 2e6fb6e2ffd2..4f89b9eaf028 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -284,6 +284,8 @@ static int evm_protected_xattr_common(const char *req_xattr_name,
int found = 0;
struct xattr_list *xattr;
+ if (!req_xattr_name)
+ return found;
namelen = strlen(req_xattr_name);
list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) {
if (!all_xattrs && !xattr->enabled)
@@ -305,7 +307,7 @@ static int evm_protected_xattr_common(const char *req_xattr_name,
return found;
}
-static int evm_protected_xattr(const char *req_xattr_name)
+int evm_protected_xattr(const char *req_xattr_name)
{
return evm_protected_xattr_common(req_xattr_name, false);
}
@@ -841,8 +843,7 @@ int evm_inode_init_security(struct inode *inode,
struct evm_xattr *xattr_data;
int rc;
- if (!(evm_initialized & EVM_INIT_HMAC) ||
- !evm_protected_xattr(lsm_xattr->name))
+ if (!(evm_initialized & EVM_INIT_HMAC))
return 0;
xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
@@ -850,7 +851,7 @@ int evm_inode_init_security(struct inode *inode,
return -ENOMEM;
xattr_data->data.type = EVM_XATTR_HMAC;
- rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
+ rc = evm_init_hmacs(inode, lsm_xattr, xattr_data->digest);
if (rc < 0)
goto out;
diff --git a/security/security.c b/security/security.c
index 14d30fec8a00..cf11bd7d6a1b 100644
--- a/security/security.c
+++ b/security/security.c
@@ -30,7 +30,11 @@
#include <linux/msg.h>
#include <net/flow.h>
-#define MAX_LSM_EVM_XATTR 2
+#define MAX_LSM_EVM_XATTR \
+ ((IS_ENABLED(CONFIG_EVM) ? 1 : 0) + \
+ (IS_ENABLED(CONFIG_SECURITY_SELINUX) ? 1 : 0) + \
+ (IS_ENABLED(CONFIG_SECURITY_SMACK) ? 1 : 0) + \
+ (IS_ENABLED(CONFIG_BPF_LSM) ? 1 : 0))
/* How many LSMs were built into the kernel? */
#define LSM_COUNT (__end_lsm_info - __start_lsm_info)
@@ -1091,9 +1095,11 @@ int security_inode_init_security(struct inode *inode, struct inode *dir,
const struct qstr *qstr,
const initxattrs initxattrs, void *fs_data)
{
+ int i = 0;
+ int ret = -EOPNOTSUPP;
struct xattr new_xattrs[MAX_LSM_EVM_XATTR + 1];
struct xattr *lsm_xattr, *evm_xattr, *xattr;
- int ret;
+ struct security_hook_list *hook_ptr;
if (unlikely(IS_PRIVATE(inode)))
return 0;
@@ -1103,15 +1109,23 @@ int security_inode_init_security(struct inode *inode, struct inode *dir,
dir, qstr, NULL, NULL, NULL);
memset(new_xattrs, 0, sizeof(new_xattrs));
lsm_xattr = new_xattrs;
- ret = call_int_hook(inode_init_security, -EOPNOTSUPP, inode, dir, qstr,
- &lsm_xattr->name,
- &lsm_xattr->value,
- &lsm_xattr->value_len);
+ hlist_for_each_entry(hook_ptr, &security_hook_heads.inode_init_security, list) {
+ ret = hook_ptr->hook.inode_init_security(inode, dir, qstr, &lsm_xattr->name,
+ &lsm_xattr->value, &lsm_xattr->value_len);
+ if (ret == -EOPNOTSUPP)
+ continue;
+ if (WARN_ON_ONCE(i >= MAX_LSM_EVM_XATTR))
+ ret = -ENOMEM;
+ if (ret != 0)
+ break;
+ lsm_xattr++;
+ i++;
+ }
if (ret)
goto out;
evm_xattr = lsm_xattr + 1;
- ret = evm_inode_init_security(inode, lsm_xattr, evm_xattr);
+ ret = evm_inode_init_security(inode, new_xattrs, evm_xattr);
if (ret)
goto out;
ret = initxattrs(inode, new_xattrs, fs_data);
--
2.38.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2] evm: Correct inode_init_security hooks behaviors
2022-10-21 15:14 [PATCH v2] evm: Correct inode_init_security hooks behaviors Nicolas Bouchinet
@ 2022-10-21 15:42 ` Casey Schaufler
2022-10-24 12:28 ` Nicolas Bouchinet
0 siblings, 1 reply; 3+ messages in thread
From: Casey Schaufler @ 2022-10-21 15:42 UTC (permalink / raw)
To: Nicolas Bouchinet, linux-integrity
Cc: philippe.trebuchet, zohar, dmitry.kasatkin, paul, jmorris, serge,
davem, lucien.xin, vgoyal, omosnace, mortonm, nicolas.bouchinet,
mic, cgzones, linux-security-module, casey
On 10/21/2022 8:14 AM, Nicolas Bouchinet wrote:
> From: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr>
>
> Fixes a NULL pointer dereference occurring in the
> `evm_protected_xattr_common` function of the EVM LSM. The bug is
> triggered if a `inode_init_security` hook returns 0 without initializing
> the given `struct xattr` fields (which is the case of BPF) and if no
> other LSM overrides thoses fields after. This also leads to memory
> leaks.
>
> Adds a `call_int_hook_xattr` macro that fetches and feed the
> `new_xattrs` array with every called hook xattr values.
>
> Adds a `evm_init_hmacs` function which init the EVM hmac using every
> entry of the array contrary to `evm_init_hmac`.
>
> Fixes the `evm_inode_init_security` function to use `evm_init_hmacs`.
>
> The `MAX_LSM_EVM_XATTR` value has been raised to 5 which gives room for
> SMACK, SELinux, Apparmor, BPF and IMA/EVM security attributes.
This does not match the code, which sets the value based on the
security modules compiled in rather than the constant 5.
>
> Changes the default return value of the `inode_init_security` hook
> definition to `-EOPNOTSUPP`.
>
> Changes the hook documentation to match the behavior of the LSMs using
> it (only xattr->value is initialised with kmalloc and thus is the only
> one that should be kfreed by the caller).
>
> Cc: stable@vger.kernel.org
> Signed-off-by: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr>
> ---
>
> Changes since v1:
> https://lore.kernel.org/linux-integrity/Y1FTSIo+1x+4X0LS@archlinux/
> * The `call_int_hook_xattr` macro has been inlined into the
> `security_inode_init_security` hook (as suggested by Paul Moor,
> Mickaël Salaün and Casey Schaufler).
> * The MAX_LSM_EVM_XATTR value is processed based on compiled LSMs (as
> proposed by Casey Schaufler).
> * Various typos and cosmetic changes has been fixed (as suggested by
> Mickaël Salaün)
> * A MAX_LSM_EVM_XATTR test has been wrapped in a WAN_ON_ONCE macro (as
> suggested by Mickaël Salaün).
> ---
> include/linux/lsm_hook_defs.h | 2 +-
> include/linux/lsm_hooks.h | 4 ++--
> security/integrity/evm/evm.h | 2 ++
> security/integrity/evm/evm_crypto.c | 22 ++++++++++++++++++++++
> security/integrity/evm/evm_main.c | 9 +++++----
> security/security.c | 28 +++++++++++++++++++++-------
> 6 files changed, 53 insertions(+), 14 deletions(-)
>
> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> index 806448173033..e5dd0c0f6345 100644
> --- a/include/linux/lsm_hook_defs.h
> +++ b/include/linux/lsm_hook_defs.h
> @@ -111,7 +111,7 @@ LSM_HOOK(int, 0, path_notify, const struct path *path, u64 mask,
> unsigned int obj_type)
> LSM_HOOK(int, 0, inode_alloc_security, struct inode *inode)
> LSM_HOOK(void, LSM_RET_VOID, inode_free_security, struct inode *inode)
> -LSM_HOOK(int, 0, inode_init_security, struct inode *inode,
> +LSM_HOOK(int, -EOPNOTSUPP, inode_init_security, struct inode *inode,
> struct inode *dir, const struct qstr *qstr, const char **name,
> void **value, size_t *len)
> LSM_HOOK(int, 0, inode_init_security_anon, struct inode *inode,
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index 84a0d7e02176..95aff9383de1 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -229,8 +229,8 @@
> * This hook is called by the fs code as part of the inode creation
> * transaction and provides for atomic labeling of the inode, unlike
> * the post_create/mkdir/... hooks called by the VFS. The hook function
> - * is expected to allocate the name and value via kmalloc, with the caller
> - * being responsible for calling kfree after using them.
> + * is expected to allocate the value via kmalloc, with the caller
> + * being responsible for calling kfree after using it.
> * If the security module does not use security attributes or does
> * not wish to put a security attribute on this particular inode,
> * then it should return -EOPNOTSUPP to skip this processing.
> diff --git a/security/integrity/evm/evm.h b/security/integrity/evm/evm.h
> index f8b8c5004fc7..a2f9886e924d 100644
> --- a/security/integrity/evm/evm.h
> +++ b/security/integrity/evm/evm.h
> @@ -60,6 +60,8 @@ int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name,
> struct evm_digest *data);
> int evm_init_hmac(struct inode *inode, const struct xattr *xattr,
> char *hmac_val);
> +int evm_init_hmacs(struct inode *inode, const struct xattr *xattrs,
> + char *hmac_val);
> int evm_init_secfs(void);
>
> #endif
> diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
> index 708de9656bbd..db6868875e09 100644
> --- a/security/integrity/evm/evm_crypto.c
> +++ b/security/integrity/evm/evm_crypto.c
> @@ -385,6 +385,28 @@ int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
> return rc;
> }
>
> +int evm_protected_xattr(const char *req_xattr_name);
> +
> +int evm_init_hmacs(struct inode *inode, const struct xattr *lsm_xattrs,
> + char *hmac_val)
> +{
> + struct shash_desc *desc;
> +
> + desc = init_desc(EVM_XATTR_HMAC, HASH_ALGO_SHA1);
> + if (IS_ERR(desc)) {
> + pr_info("init_desc failed\n");
> + return PTR_ERR(desc);
> + }
> +
> + for (int i = 0; lsm_xattrs[i].value != NULL; i++) {
> + if (evm_protected_xattr(lsm_xattrs[i].name))
> + crypto_shash_update(desc, lsm_xattrs[i].value, lsm_xattrs[i].value_len);
> + }
> + hmac_add_misc(desc, inode, EVM_XATTR_HMAC, hmac_val);
> + kfree(desc);
> + return 0;
> +}
> +
> int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattr,
> char *hmac_val)
> {
> diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
> index 2e6fb6e2ffd2..4f89b9eaf028 100644
> --- a/security/integrity/evm/evm_main.c
> +++ b/security/integrity/evm/evm_main.c
> @@ -284,6 +284,8 @@ static int evm_protected_xattr_common(const char *req_xattr_name,
> int found = 0;
> struct xattr_list *xattr;
>
> + if (!req_xattr_name)
> + return found;
> namelen = strlen(req_xattr_name);
> list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) {
> if (!all_xattrs && !xattr->enabled)
> @@ -305,7 +307,7 @@ static int evm_protected_xattr_common(const char *req_xattr_name,
> return found;
> }
>
> -static int evm_protected_xattr(const char *req_xattr_name)
> +int evm_protected_xattr(const char *req_xattr_name)
> {
> return evm_protected_xattr_common(req_xattr_name, false);
> }
> @@ -841,8 +843,7 @@ int evm_inode_init_security(struct inode *inode,
> struct evm_xattr *xattr_data;
> int rc;
>
> - if (!(evm_initialized & EVM_INIT_HMAC) ||
> - !evm_protected_xattr(lsm_xattr->name))
> + if (!(evm_initialized & EVM_INIT_HMAC))
> return 0;
>
> xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
> @@ -850,7 +851,7 @@ int evm_inode_init_security(struct inode *inode,
> return -ENOMEM;
>
> xattr_data->data.type = EVM_XATTR_HMAC;
> - rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
> + rc = evm_init_hmacs(inode, lsm_xattr, xattr_data->digest);
> if (rc < 0)
> goto out;
>
> diff --git a/security/security.c b/security/security.c
> index 14d30fec8a00..cf11bd7d6a1b 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -30,7 +30,11 @@
> #include <linux/msg.h>
> #include <net/flow.h>
>
> -#define MAX_LSM_EVM_XATTR 2
> +#define MAX_LSM_EVM_XATTR \
> + ((IS_ENABLED(CONFIG_EVM) ? 1 : 0) + \
> + (IS_ENABLED(CONFIG_SECURITY_SELINUX) ? 1 : 0) + \
> + (IS_ENABLED(CONFIG_SECURITY_SMACK) ? 1 : 0) + \
> + (IS_ENABLED(CONFIG_BPF_LSM) ? 1 : 0))
>
> /* How many LSMs were built into the kernel? */
> #define LSM_COUNT (__end_lsm_info - __start_lsm_info)
> @@ -1091,9 +1095,11 @@ int security_inode_init_security(struct inode *inode, struct inode *dir,
> const struct qstr *qstr,
> const initxattrs initxattrs, void *fs_data)
> {
> + int i = 0;
> + int ret = -EOPNOTSUPP;
> struct xattr new_xattrs[MAX_LSM_EVM_XATTR + 1];
> struct xattr *lsm_xattr, *evm_xattr, *xattr;
> - int ret;
> + struct security_hook_list *hook_ptr;
>
> if (unlikely(IS_PRIVATE(inode)))
> return 0;
> @@ -1103,15 +1109,23 @@ int security_inode_init_security(struct inode *inode, struct inode *dir,
> dir, qstr, NULL, NULL, NULL);
> memset(new_xattrs, 0, sizeof(new_xattrs));
> lsm_xattr = new_xattrs;
> - ret = call_int_hook(inode_init_security, -EOPNOTSUPP, inode, dir, qstr,
> - &lsm_xattr->name,
> - &lsm_xattr->value,
> - &lsm_xattr->value_len);
> + hlist_for_each_entry(hook_ptr, &security_hook_heads.inode_init_security, list) {
> + ret = hook_ptr->hook.inode_init_security(inode, dir, qstr, &lsm_xattr->name,
> + &lsm_xattr->value, &lsm_xattr->value_len);
> + if (ret == -EOPNOTSUPP)
> + continue;
> + if (WARN_ON_ONCE(i >= MAX_LSM_EVM_XATTR))
> + ret = -ENOMEM;
> + if (ret != 0)
> + break;
> + lsm_xattr++;
> + i++;
> + }
> if (ret)
> goto out;
>
> evm_xattr = lsm_xattr + 1;
> - ret = evm_inode_init_security(inode, lsm_xattr, evm_xattr);
> + ret = evm_inode_init_security(inode, new_xattrs, evm_xattr);
> if (ret)
> goto out;
> ret = initxattrs(inode, new_xattrs, fs_data);
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] evm: Correct inode_init_security hooks behaviors
2022-10-21 15:42 ` Casey Schaufler
@ 2022-10-24 12:28 ` Nicolas Bouchinet
0 siblings, 0 replies; 3+ messages in thread
From: Nicolas Bouchinet @ 2022-10-24 12:28 UTC (permalink / raw)
To: Casey Schaufler
Cc: linux-integrity, philippe.trebuchet, zohar, dmitry.kasatkin,
paul, jmorris, serge, davem, lucien.xin, vgoyal, omosnace,
mortonm, nicolas.bouchinet, mic, cgzones, linux-security-module
Hi Casey, thanks again for your time,
On Fri, Oct 21, 2022 at 08:42:20AM -0700, Casey Schaufler wrote:
> On 10/21/2022 8:14 AM, Nicolas Bouchinet wrote:
> > From: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr>
> >
> > Fixes a NULL pointer dereference occurring in the
> > `evm_protected_xattr_common` function of the EVM LSM. The bug is
> > triggered if a `inode_init_security` hook returns 0 without initializing
> > the given `struct xattr` fields (which is the case of BPF) and if no
> > other LSM overrides thoses fields after. This also leads to memory
> > leaks.
> >
> > Adds a `call_int_hook_xattr` macro that fetches and feed the
> > `new_xattrs` array with every called hook xattr values.
> >
> > Adds a `evm_init_hmacs` function which init the EVM hmac using every
> > entry of the array contrary to `evm_init_hmac`.
> >
> > Fixes the `evm_inode_init_security` function to use `evm_init_hmacs`.
> >
> > The `MAX_LSM_EVM_XATTR` value has been raised to 5 which gives room for
> > SMACK, SELinux, Apparmor, BPF and IMA/EVM security attributes.
>
> This does not match the code, which sets the value based on the
> security modules compiled in rather than the constant 5.
>
Sorry for this, I think I will wait a day before sending patch v3.
> >
> > Changes the default return value of the `inode_init_security` hook
> > definition to `-EOPNOTSUPP`.
> >
> > Changes the hook documentation to match the behavior of the LSMs using
> > it (only xattr->value is initialised with kmalloc and thus is the only
> > one that should be kfreed by the caller).
> >
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr>
> > ---
> >
> > Changes since v1:
> > https://lore.kernel.org/linux-integrity/Y1FTSIo+1x+4X0LS@archlinux/
> > * The `call_int_hook_xattr` macro has been inlined into the
> > `security_inode_init_security` hook (as suggested by Paul Moor,
> > Mickaël Salaün and Casey Schaufler).
> > * The MAX_LSM_EVM_XATTR value is processed based on compiled LSMs (as
> > proposed by Casey Schaufler).
> > * Various typos and cosmetic changes has been fixed (as suggested by
> > Mickaël Salaün)
> > * A MAX_LSM_EVM_XATTR test has been wrapped in a WAN_ON_ONCE macro (as
> > suggested by Mickaël Salaün).
> > ---
> > include/linux/lsm_hook_defs.h | 2 +-
> > include/linux/lsm_hooks.h | 4 ++--
> > security/integrity/evm/evm.h | 2 ++
> > security/integrity/evm/evm_crypto.c | 22 ++++++++++++++++++++++
> > security/integrity/evm/evm_main.c | 9 +++++----
> > security/security.c | 28 +++++++++++++++++++++-------
> > 6 files changed, 53 insertions(+), 14 deletions(-)
> >
> > diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> > index 806448173033..e5dd0c0f6345 100644
> > --- a/include/linux/lsm_hook_defs.h
> > +++ b/include/linux/lsm_hook_defs.h
> > @@ -111,7 +111,7 @@ LSM_HOOK(int, 0, path_notify, const struct path *path, u64 mask,
> > unsigned int obj_type)
> > LSM_HOOK(int, 0, inode_alloc_security, struct inode *inode)
> > LSM_HOOK(void, LSM_RET_VOID, inode_free_security, struct inode *inode)
> > -LSM_HOOK(int, 0, inode_init_security, struct inode *inode,
> > +LSM_HOOK(int, -EOPNOTSUPP, inode_init_security, struct inode *inode,
> > struct inode *dir, const struct qstr *qstr, const char **name,
> > void **value, size_t *len)
> > LSM_HOOK(int, 0, inode_init_security_anon, struct inode *inode,
> > diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> > index 84a0d7e02176..95aff9383de1 100644
> > --- a/include/linux/lsm_hooks.h
> > +++ b/include/linux/lsm_hooks.h
> > @@ -229,8 +229,8 @@
> > * This hook is called by the fs code as part of the inode creation
> > * transaction and provides for atomic labeling of the inode, unlike
> > * the post_create/mkdir/... hooks called by the VFS. The hook function
> > - * is expected to allocate the name and value via kmalloc, with the caller
> > - * being responsible for calling kfree after using them.
> > + * is expected to allocate the value via kmalloc, with the caller
> > + * being responsible for calling kfree after using it.
> > * If the security module does not use security attributes or does
> > * not wish to put a security attribute on this particular inode,
> > * then it should return -EOPNOTSUPP to skip this processing.
> > diff --git a/security/integrity/evm/evm.h b/security/integrity/evm/evm.h
> > index f8b8c5004fc7..a2f9886e924d 100644
> > --- a/security/integrity/evm/evm.h
> > +++ b/security/integrity/evm/evm.h
> > @@ -60,6 +60,8 @@ int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name,
> > struct evm_digest *data);
> > int evm_init_hmac(struct inode *inode, const struct xattr *xattr,
> > char *hmac_val);
> > +int evm_init_hmacs(struct inode *inode, const struct xattr *xattrs,
> > + char *hmac_val);
> > int evm_init_secfs(void);
> >
> > #endif
> > diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
> > index 708de9656bbd..db6868875e09 100644
> > --- a/security/integrity/evm/evm_crypto.c
> > +++ b/security/integrity/evm/evm_crypto.c
> > @@ -385,6 +385,28 @@ int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
> > return rc;
> > }
> >
> > +int evm_protected_xattr(const char *req_xattr_name);
> > +
> > +int evm_init_hmacs(struct inode *inode, const struct xattr *lsm_xattrs,
> > + char *hmac_val)
> > +{
> > + struct shash_desc *desc;
> > +
> > + desc = init_desc(EVM_XATTR_HMAC, HASH_ALGO_SHA1);
> > + if (IS_ERR(desc)) {
> > + pr_info("init_desc failed\n");
> > + return PTR_ERR(desc);
> > + }
> > +
> > + for (int i = 0; lsm_xattrs[i].value != NULL; i++) {
> > + if (evm_protected_xattr(lsm_xattrs[i].name))
> > + crypto_shash_update(desc, lsm_xattrs[i].value, lsm_xattrs[i].value_len);
> > + }
> > + hmac_add_misc(desc, inode, EVM_XATTR_HMAC, hmac_val);
> > + kfree(desc);
> > + return 0;
> > +}
> > +
> > int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattr,
> > char *hmac_val)
> > {
> > diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
> > index 2e6fb6e2ffd2..4f89b9eaf028 100644
> > --- a/security/integrity/evm/evm_main.c
> > +++ b/security/integrity/evm/evm_main.c
> > @@ -284,6 +284,8 @@ static int evm_protected_xattr_common(const char *req_xattr_name,
> > int found = 0;
> > struct xattr_list *xattr;
> >
> > + if (!req_xattr_name)
> > + return found;
> > namelen = strlen(req_xattr_name);
> > list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) {
> > if (!all_xattrs && !xattr->enabled)
> > @@ -305,7 +307,7 @@ static int evm_protected_xattr_common(const char *req_xattr_name,
> > return found;
> > }
> >
> > -static int evm_protected_xattr(const char *req_xattr_name)
> > +int evm_protected_xattr(const char *req_xattr_name)
> > {
> > return evm_protected_xattr_common(req_xattr_name, false);
> > }
> > @@ -841,8 +843,7 @@ int evm_inode_init_security(struct inode *inode,
> > struct evm_xattr *xattr_data;
> > int rc;
> >
> > - if (!(evm_initialized & EVM_INIT_HMAC) ||
> > - !evm_protected_xattr(lsm_xattr->name))
> > + if (!(evm_initialized & EVM_INIT_HMAC))
> > return 0;
> >
> > xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
> > @@ -850,7 +851,7 @@ int evm_inode_init_security(struct inode *inode,
> > return -ENOMEM;
> >
> > xattr_data->data.type = EVM_XATTR_HMAC;
> > - rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
> > + rc = evm_init_hmacs(inode, lsm_xattr, xattr_data->digest);
> > if (rc < 0)
> > goto out;
> >
> > diff --git a/security/security.c b/security/security.c
> > index 14d30fec8a00..cf11bd7d6a1b 100644
> > --- a/security/security.c
> > +++ b/security/security.c
> > @@ -30,7 +30,11 @@
> > #include <linux/msg.h>
> > #include <net/flow.h>
> >
> > -#define MAX_LSM_EVM_XATTR 2
> > +#define MAX_LSM_EVM_XATTR \
> > + ((IS_ENABLED(CONFIG_EVM) ? 1 : 0) + \
> > + (IS_ENABLED(CONFIG_SECURITY_SELINUX) ? 1 : 0) + \
> > + (IS_ENABLED(CONFIG_SECURITY_SMACK) ? 1 : 0) + \
> > + (IS_ENABLED(CONFIG_BPF_LSM) ? 1 : 0))
> >
> > /* How many LSMs were built into the kernel? */
> > #define LSM_COUNT (__end_lsm_info - __start_lsm_info)
> > @@ -1091,9 +1095,11 @@ int security_inode_init_security(struct inode *inode, struct inode *dir,
> > const struct qstr *qstr,
> > const initxattrs initxattrs, void *fs_data)
> > {
> > + int i = 0;
> > + int ret = -EOPNOTSUPP;
> > struct xattr new_xattrs[MAX_LSM_EVM_XATTR + 1];
> > struct xattr *lsm_xattr, *evm_xattr, *xattr;
> > - int ret;
> > + struct security_hook_list *hook_ptr;
> >
> > if (unlikely(IS_PRIVATE(inode)))
> > return 0;
> > @@ -1103,15 +1109,23 @@ int security_inode_init_security(struct inode *inode, struct inode *dir,
> > dir, qstr, NULL, NULL, NULL);
> > memset(new_xattrs, 0, sizeof(new_xattrs));
> > lsm_xattr = new_xattrs;
> > - ret = call_int_hook(inode_init_security, -EOPNOTSUPP, inode, dir, qstr,
> > - &lsm_xattr->name,
> > - &lsm_xattr->value,
> > - &lsm_xattr->value_len);
> > + hlist_for_each_entry(hook_ptr, &security_hook_heads.inode_init_security, list) {
> > + ret = hook_ptr->hook.inode_init_security(inode, dir, qstr, &lsm_xattr->name,
> > + &lsm_xattr->value, &lsm_xattr->value_len);
> > + if (ret == -EOPNOTSUPP)
> > + continue;
> > + if (WARN_ON_ONCE(i >= MAX_LSM_EVM_XATTR))
> > + ret = -ENOMEM;
> > + if (ret != 0)
> > + break;
> > + lsm_xattr++;
> > + i++;
> > + }
> > if (ret)
> > goto out;
> >
> > evm_xattr = lsm_xattr + 1;
> > - ret = evm_inode_init_security(inode, lsm_xattr, evm_xattr);
> > + ret = evm_inode_init_security(inode, new_xattrs, evm_xattr);
> > if (ret)
> > goto out;
> > ret = initxattrs(inode, new_xattrs, fs_data);
Best regards,
Nicolas Bouchinet
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2022-10-24 19:19 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2022-10-21 15:14 [PATCH v2] evm: Correct inode_init_security hooks behaviors Nicolas Bouchinet
2022-10-21 15:42 ` Casey Schaufler
2022-10-24 12:28 ` Nicolas Bouchinet
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