[PATCH] ima: Avoid blocking in RCU read-side critical section

[PATCH] ima: Avoid blocking in RCU read-side critical section

[Roberto Sassu]

From: GUO Zihua <guozihua@huawei.com>

A panic happens in ima_match_policy:

BUG: unable to handle kernel NULL pointer dereference at 0000000000000010
PGD 42f873067 P4D 0
Oops: 0000 [#1] SMP NOPTI
CPU: 5 PID: 1286325 Comm: kubeletmonit.sh
Kdump: loaded Tainted: P
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
               BIOS 0.0.0 02/06/2015
RIP: 0010:ima_match_policy+0x84/0x450
Code: 49 89 fc 41 89 cf 31 ed 89 44 24 14 eb 1c 44 39
      7b 18 74 26 41 83 ff 05 74 20 48 8b 1b 48 3b 1d
      f2 b9 f4 00 0f 84 9c 01 00 00 <44> 85 73 10 74 ea
      44 8b 6b 14 41 f6 c5 01 75 d4 41 f6 c5 02 74 0f
RSP: 0018:ff71570009e07a80 EFLAGS: 00010207
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000200
RDX: ffffffffad8dc7c0 RSI: 0000000024924925 RDI: ff3e27850dea2000
RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffffabfce739
R10: ff3e27810cc42400 R11: 0000000000000000 R12: ff3e2781825ef970
R13: 00000000ff3e2785 R14: 000000000000000c R15: 0000000000000001
FS:  00007f5195b51740(0000)
GS:ff3e278b12d40000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000010 CR3: 0000000626d24002 CR4: 0000000000361ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 ima_get_action+0x22/0x30
 process_measurement+0xb0/0x830
 ? page_add_file_rmap+0x15/0x170
 ? alloc_set_pte+0x269/0x4c0
 ? prep_new_page+0x81/0x140
 ? simple_xattr_get+0x75/0xa0
 ? selinux_file_open+0x9d/0xf0
 ima_file_check+0x64/0x90
 path_openat+0x571/0x1720
 do_filp_open+0x9b/0x110
 ? page_counter_try_charge+0x57/0xc0
 ? files_cgroup_alloc_fd+0x38/0x60
 ? __alloc_fd+0xd4/0x250
 ? do_sys_open+0x1bd/0x250
 do_sys_open+0x1bd/0x250
 do_syscall_64+0x5d/0x1d0
 entry_SYSCALL_64_after_hwframe+0x65/0xca

Commit c7423dbdbc9e ("ima: Handle -ESTALE returned by
ima_filter_rule_match()") introduced call to ima_lsm_copy_rule within a
RCU read-side critical section which contains kmalloc with GFP_KERNEL.
This implies a possible sleep and violates limitations of RCU read-side
critical sections on non-PREEMPT systems.

Sleeping within RCU read-side critical section might cause
synchronize_rcu() returning early and break RCU protection, allowing a
UAF to happen.

The root cause of this issue could be described as follows:
|	Thread A	|	Thread B	|
|			|ima_match_policy	|
|			|  rcu_read_lock	|
|ima_lsm_update_rule	|			|
|  synchronize_rcu	|			|
|			|    kmalloc(GFP_KERNEL)|
|			|      sleep		|
==> synchronize_rcu returns early
|  kfree(entry)		|			|
|			|    entry = entry->next|
==> UAF happens and entry now becomes NULL (or could be anything).
|			|    entry->action	|
==> Accessing entry might cause panic.

To fix this issue, we are converting all kmalloc that is called within
RCU read-side critical section to use GFP_ATOMIC.

Fixes: c7423dbdbc9e ("ima: Handle -ESTALE returned by ima_filter_rule_match()")
Cc: stable@vger.kernel.org
Signed-off-by: GUO Zihua <guozihua@huawei.com>
Acked-by: John Johansen <john.johansen@canonical.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
[PM: fixed missing comment, long lines, !CONFIG_IMA_LSM_RULES case]
Signed-off-by: Paul Moore <paul@paul-moore.com>
(cherry picked from commit 9a95c5bfbf02a0a7f5983280fe284a0ff0836c34)
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---
Backporting notes:
- Remove security_audit_rule_init() documentation changes
- Add default return value parameter to call_int_hook()
  in security_audit_rule_init()
- Can be backported to 6.1.x, 5.15.x, 5.10.x

 include/linux/lsm_hook_defs.h       |  2 +-
 include/linux/security.h            |  5 +++--
 kernel/auditfilter.c                |  5 +++--
 security/apparmor/audit.c           |  6 +++---
 security/apparmor/include/audit.h   |  2 +-
 security/integrity/ima/ima.h        |  2 +-
 security/integrity/ima/ima_policy.c | 15 +++++++++------
 security/security.c                 |  6 ++++--
 security/selinux/include/audit.h    |  4 +++-
 security/selinux/ss/services.c      |  5 +++--
 security/smack/smack_lsm.c          |  4 +++-
 11 files changed, 34 insertions(+), 22 deletions(-)

diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 6239a378c0ea..0b4f7289951a 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -382,7 +382,7 @@ LSM_HOOK(int, 0, key_getsecurity, struct key *key, char **_buffer)
 
 #ifdef CONFIG_AUDIT
 LSM_HOOK(int, 0, audit_rule_init, u32 field, u32 op, char *rulestr,
-	 void **lsmrule)
+	 void **lsmrule, gfp_t gfp)
 LSM_HOOK(int, 0, audit_rule_known, struct audit_krule *krule)
 LSM_HOOK(int, 0, audit_rule_match, u32 secid, u32 field, u32 op, void *lsmrule)
 LSM_HOOK(void, LSM_RET_VOID, audit_rule_free, void *lsmrule)
diff --git a/include/linux/security.h b/include/linux/security.h
index 2772f6375f14..c33c95f409eb 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1921,7 +1921,8 @@ static inline int security_key_getsecurity(struct key *key, char **_buffer)
 
 #ifdef CONFIG_AUDIT
 #ifdef CONFIG_SECURITY
-int security_audit_rule_init(u32 field, u32 op, char *rulestr, void **lsmrule);
+int security_audit_rule_init(u32 field, u32 op, char *rulestr, void **lsmrule,
+			     gfp_t gfp);
 int security_audit_rule_known(struct audit_krule *krule);
 int security_audit_rule_match(u32 secid, u32 field, u32 op, void *lsmrule);
 void security_audit_rule_free(void *lsmrule);
@@ -1929,7 +1930,7 @@ void security_audit_rule_free(void *lsmrule);
 #else
 
 static inline int security_audit_rule_init(u32 field, u32 op, char *rulestr,
-					   void **lsmrule)
+					   void **lsmrule, gfp_t gfp)
 {
 	return 0;
 }
diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
index 42d99896e7a6..6c9a4d322309 100644
--- a/kernel/auditfilter.c
+++ b/kernel/auditfilter.c
@@ -529,7 +529,8 @@ static struct audit_entry *audit_data_to_entry(struct audit_rule_data *data,
 			entry->rule.buflen += f_val;
 			f->lsm_str = str;
 			err = security_audit_rule_init(f->type, f->op, str,
-						       (void **)&f->lsm_rule);
+						       (void **)&f->lsm_rule,
+						       GFP_KERNEL);
 			/* Keep currently invalid fields around in case they
 			 * become valid after a policy reload. */
 			if (err == -EINVAL) {
@@ -798,7 +799,7 @@ static inline int audit_dupe_lsm_field(struct audit_field *df,
 
 	/* our own (refreshed) copy of lsm_rule */
 	ret = security_audit_rule_init(df->type, df->op, df->lsm_str,
-				       (void **)&df->lsm_rule);
+				       (void **)&df->lsm_rule, GFP_KERNEL);
 	/* Keep currently invalid fields around in case they
 	 * become valid after a policy reload. */
 	if (ret == -EINVAL) {
diff --git a/security/apparmor/audit.c b/security/apparmor/audit.c
index 704b0c895605..963df28584ee 100644
--- a/security/apparmor/audit.c
+++ b/security/apparmor/audit.c
@@ -173,7 +173,7 @@ void aa_audit_rule_free(void *vrule)
 	}
 }
 
-int aa_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule)
+int aa_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule, gfp_t gfp)
 {
 	struct aa_audit_rule *rule;
 
@@ -186,14 +186,14 @@ int aa_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule)
 		return -EINVAL;
 	}
 
-	rule = kzalloc(sizeof(struct aa_audit_rule), GFP_KERNEL);
+	rule = kzalloc(sizeof(struct aa_audit_rule), gfp);
 
 	if (!rule)
 		return -ENOMEM;
 
 	/* Currently rules are treated as coming from the root ns */
 	rule->label = aa_label_parse(&root_ns->unconfined->label, rulestr,
-				     GFP_KERNEL, true, false);
+				     gfp, true, false);
 	if (IS_ERR(rule->label)) {
 		int err = PTR_ERR(rule->label);
 		aa_audit_rule_free(rule);
diff --git a/security/apparmor/include/audit.h b/security/apparmor/include/audit.h
index 18519a4eb67e..f325f1bef8d6 100644
--- a/security/apparmor/include/audit.h
+++ b/security/apparmor/include/audit.h
@@ -186,7 +186,7 @@ static inline int complain_error(int error)
 }
 
 void aa_audit_rule_free(void *vrule);
-int aa_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule);
+int aa_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule, gfp_t gfp);
 int aa_audit_rule_known(struct audit_krule *rule);
 int aa_audit_rule_match(u32 sid, u32 field, u32 op, void *vrule);
 
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index be965a8715e4..c80bc15b4486 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -428,7 +428,7 @@ static inline void ima_free_modsig(struct modsig *modsig)
 #else
 
 static inline int ima_filter_rule_init(u32 field, u32 op, char *rulestr,
-				       void **lsmrule)
+				       void **lsmrule, gfp_t gfp)
 {
 	return -EINVAL;
 }
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index bdc40535ff48..1f930711db76 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -377,7 +377,8 @@ static void ima_free_rule(struct ima_rule_entry *entry)
 	kfree(entry);
 }
 
-static struct ima_rule_entry *ima_lsm_copy_rule(struct ima_rule_entry *entry)
+static struct ima_rule_entry *ima_lsm_copy_rule(struct ima_rule_entry *entry,
+						gfp_t gfp)
 {
 	struct ima_rule_entry *nentry;
 	int i;
@@ -386,7 +387,7 @@ static struct ima_rule_entry *ima_lsm_copy_rule(struct ima_rule_entry *entry)
 	 * Immutable elements are copied over as pointers and data; only
 	 * lsm rules can change
 	 */
-	nentry = kmemdup(entry, sizeof(*nentry), GFP_KERNEL);
+	nentry = kmemdup(entry, sizeof(*nentry), gfp);
 	if (!nentry)
 		return NULL;
 
@@ -401,7 +402,8 @@ static struct ima_rule_entry *ima_lsm_copy_rule(struct ima_rule_entry *entry)
 
 		ima_filter_rule_init(nentry->lsm[i].type, Audit_equal,
 				     nentry->lsm[i].args_p,
-				     &nentry->lsm[i].rule);
+				     &nentry->lsm[i].rule,
+				     gfp);
 		if (!nentry->lsm[i].rule)
 			pr_warn("rule for LSM \'%s\' is undefined\n",
 				nentry->lsm[i].args_p);
@@ -414,7 +416,7 @@ static int ima_lsm_update_rule(struct ima_rule_entry *entry)
 	int i;
 	struct ima_rule_entry *nentry;
 
-	nentry = ima_lsm_copy_rule(entry);
+	nentry = ima_lsm_copy_rule(entry, GFP_KERNEL);
 	if (!nentry)
 		return -ENOMEM;
 
@@ -638,7 +640,7 @@ static bool ima_match_rules(struct ima_rule_entry *rule,
 		}
 
 		if (rc == -ESTALE && !rule_reinitialized) {
-			lsm_rule = ima_lsm_copy_rule(rule);
+			lsm_rule = ima_lsm_copy_rule(rule, GFP_ATOMIC);
 			if (lsm_rule) {
 				rule_reinitialized = true;
 				goto retry;
@@ -1113,7 +1115,8 @@ static int ima_lsm_rule_init(struct ima_rule_entry *entry,
 	entry->lsm[lsm_rule].type = audit_type;
 	result = ima_filter_rule_init(entry->lsm[lsm_rule].type, Audit_equal,
 				      entry->lsm[lsm_rule].args_p,
-				      &entry->lsm[lsm_rule].rule);
+				      &entry->lsm[lsm_rule].rule,
+				      GFP_KERNEL);
 	if (!entry->lsm[lsm_rule].rule) {
 		pr_warn("rule for LSM \'%s\' is undefined\n",
 			entry->lsm[lsm_rule].args_p);
diff --git a/security/security.c b/security/security.c
index 1b504c296551..fb1692254851 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2617,9 +2617,11 @@ int security_key_getsecurity(struct key *key, char **_buffer)
 
 #ifdef CONFIG_AUDIT
 
-int security_audit_rule_init(u32 field, u32 op, char *rulestr, void **lsmrule)
+int security_audit_rule_init(u32 field, u32 op, char *rulestr, void **lsmrule,
+			     gfp_t gfp)
 {
-	return call_int_hook(audit_rule_init, 0, field, op, rulestr, lsmrule);
+	return call_int_hook(audit_rule_init, 0, field, op, rulestr, lsmrule,
+			     gfp);
 }
 
 int security_audit_rule_known(struct audit_krule *krule)
diff --git a/security/selinux/include/audit.h b/security/selinux/include/audit.h
index 406bceb90c6c..ef54f61a3066 100644
--- a/security/selinux/include/audit.h
+++ b/security/selinux/include/audit.h
@@ -21,12 +21,14 @@
  *	@op: the operator the rule uses
  *	@rulestr: the text "target" of the rule
  *	@rule: pointer to the new rule structure returned via this
+ *	@gfp: GFP flag used for kmalloc
  *
  *	Returns 0 if successful, -errno if not.  On success, the rule structure
  *	will be allocated internally.  The caller must free this structure with
  *	selinux_audit_rule_free() after use.
  */
-int selinux_audit_rule_init(u32 field, u32 op, char *rulestr, void **rule);
+int selinux_audit_rule_init(u32 field, u32 op, char *rulestr, void **rule,
+			    gfp_t gfp);
 
 /**
  *	selinux_audit_rule_free - free an selinux audit rule structure.
diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index 64a6a37dc36d..2b8ebd390e37 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -3563,7 +3563,8 @@ void selinux_audit_rule_free(void *vrule)
 	}
 }
 
-int selinux_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule)
+int selinux_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule,
+			    gfp_t gfp)
 {
 	struct selinux_state *state = &selinux_state;
 	struct selinux_policy *policy;
@@ -3604,7 +3605,7 @@ int selinux_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule)
 		return -EINVAL;
 	}
 
-	tmprule = kzalloc(sizeof(struct selinux_audit_rule), GFP_KERNEL);
+	tmprule = kzalloc(sizeof(struct selinux_audit_rule), gfp);
 	if (!tmprule)
 		return -ENOMEM;
 
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index feba69549d08..b0a483e40c82 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -4552,11 +4552,13 @@ static int smack_post_notification(const struct cred *w_cred,
  * @op: required testing operator (=, !=, >, <, ...)
  * @rulestr: smack label to be audited
  * @vrule: pointer to save our own audit rule representation
+ * @gfp: type of the memory for the allocation
  *
  * Prepare to audit cases where (@field @op @rulestr) is true.
  * The label to be audited is created if necessay.
  */
-static int smack_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule)
+static int smack_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule,
+				 gfp_t gfp)
 {
 	struct smack_known *skp;
 	char **rule = (char **)vrule;
-- 
2.34.1

Re: [PATCH] ima: Avoid blocking in RCU read-side critical section

[Paul Moore]

On Thu, Jul 4, 2024 at 6:43 AM Roberto Sassu
<roberto.sassu@huaweicloud.com> wrote:
>
> From: GUO Zihua <guozihua@huawei.com>
>
> A panic happens in ima_match_policy:
>
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000010
> PGD 42f873067 P4D 0
> Oops: 0000 [#1] SMP NOPTI
> CPU: 5 PID: 1286325 Comm: kubeletmonit.sh
> Kdump: loaded Tainted: P
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
>                BIOS 0.0.0 02/06/2015
> RIP: 0010:ima_match_policy+0x84/0x450
> Code: 49 89 fc 41 89 cf 31 ed 89 44 24 14 eb 1c 44 39
>       7b 18 74 26 41 83 ff 05 74 20 48 8b 1b 48 3b 1d
>       f2 b9 f4 00 0f 84 9c 01 00 00 <44> 85 73 10 74 ea
>       44 8b 6b 14 41 f6 c5 01 75 d4 41 f6 c5 02 74 0f
> RSP: 0018:ff71570009e07a80 EFLAGS: 00010207
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000200
> RDX: ffffffffad8dc7c0 RSI: 0000000024924925 RDI: ff3e27850dea2000
> RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffffabfce739
> R10: ff3e27810cc42400 R11: 0000000000000000 R12: ff3e2781825ef970
> R13: 00000000ff3e2785 R14: 000000000000000c R15: 0000000000000001
> FS:  00007f5195b51740(0000)
> GS:ff3e278b12d40000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000010 CR3: 0000000626d24002 CR4: 0000000000361ee0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  ima_get_action+0x22/0x30
>  process_measurement+0xb0/0x830
>  ? page_add_file_rmap+0x15/0x170
>  ? alloc_set_pte+0x269/0x4c0
>  ? prep_new_page+0x81/0x140
>  ? simple_xattr_get+0x75/0xa0
>  ? selinux_file_open+0x9d/0xf0
>  ima_file_check+0x64/0x90
>  path_openat+0x571/0x1720
>  do_filp_open+0x9b/0x110
>  ? page_counter_try_charge+0x57/0xc0
>  ? files_cgroup_alloc_fd+0x38/0x60
>  ? __alloc_fd+0xd4/0x250
>  ? do_sys_open+0x1bd/0x250
>  do_sys_open+0x1bd/0x250
>  do_syscall_64+0x5d/0x1d0
>  entry_SYSCALL_64_after_hwframe+0x65/0xca
>
> Commit c7423dbdbc9e ("ima: Handle -ESTALE returned by
> ima_filter_rule_match()") introduced call to ima_lsm_copy_rule within a
> RCU read-side critical section which contains kmalloc with GFP_KERNEL.
> This implies a possible sleep and violates limitations of RCU read-side
> critical sections on non-PREEMPT systems.
>
> Sleeping within RCU read-side critical section might cause
> synchronize_rcu() returning early and break RCU protection, allowing a
> UAF to happen.
>
> The root cause of this issue could be described as follows:
> |       Thread A        |       Thread B        |
> |                       |ima_match_policy       |
> |                       |  rcu_read_lock        |
> |ima_lsm_update_rule    |                       |
> |  synchronize_rcu      |                       |
> |                       |    kmalloc(GFP_KERNEL)|
> |                       |      sleep            |
> ==> synchronize_rcu returns early
> |  kfree(entry)         |                       |
> |                       |    entry = entry->next|
> ==> UAF happens and entry now becomes NULL (or could be anything).
> |                       |    entry->action      |
> ==> Accessing entry might cause panic.
>
> To fix this issue, we are converting all kmalloc that is called within
> RCU read-side critical section to use GFP_ATOMIC.
>
> Fixes: c7423dbdbc9e ("ima: Handle -ESTALE returned by ima_filter_rule_match()")
> Cc: stable@vger.kernel.org
> Signed-off-by: GUO Zihua <guozihua@huawei.com>
> Acked-by: John Johansen <john.johansen@canonical.com>
> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
> Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
> [PM: fixed missing comment, long lines, !CONFIG_IMA_LSM_RULES case]
> Signed-off-by: Paul Moore <paul@paul-moore.com>
> (cherry picked from commit 9a95c5bfbf02a0a7f5983280fe284a0ff0836c34)
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> ---
> Backporting notes:
> - Remove security_audit_rule_init() documentation changes
> - Add default return value parameter to call_int_hook()
>   in security_audit_rule_init()
> - Can be backported to 6.1.x, 5.15.x, 5.10.x
>
>  include/linux/lsm_hook_defs.h       |  2 +-
>  include/linux/security.h            |  5 +++--
>  kernel/auditfilter.c                |  5 +++--
>  security/apparmor/audit.c           |  6 +++---
>  security/apparmor/include/audit.h   |  2 +-
>  security/integrity/ima/ima.h        |  2 +-
>  security/integrity/ima/ima_policy.c | 15 +++++++++------
>  security/security.c                 |  6 ++++--
>  security/selinux/include/audit.h    |  4 +++-
>  security/selinux/ss/services.c      |  5 +++--
>  security/smack/smack_lsm.c          |  4 +++-
>  11 files changed, 34 insertions(+), 22 deletions(-)

This looks like a reasonable backport to me, thanks Roberto.

Reviewed-by: Paul Moore <paul@paul-moore.com>

Stable folks, the original commit ID is somewhat hidden in the
metadata above, but the original patch is 9a95c5bfbf02 ("ima: Avoid
blocking in RCU read-side critical section")
and it is present in Linus' tree starting with v6.10-rc5.

-- 
paul-moore.com

Re: [PATCH] ima: Avoid blocking in RCU read-side critical section

[Mimi Zohar]

On Thu, 2024-07-04 at 12:43 +0200, Roberto Sassu wrote:
> From: GUO Zihua <guozihua@huawei.com>
> 
> A panic happens in ima_match_policy:
> 
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000010
> PGD 42f873067 P4D 0
> Oops: 0000 [#1] SMP NOPTI
> CPU: 5 PID: 1286325 Comm: kubeletmonit.sh
> Kdump: loaded Tainted: P
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
>                BIOS 0.0.0 02/06/2015
> RIP: 0010:ima_match_policy+0x84/0x450
> Code: 49 89 fc 41 89 cf 31 ed 89 44 24 14 eb 1c 44 39
>       7b 18 74 26 41 83 ff 05 74 20 48 8b 1b 48 3b 1d
>       f2 b9 f4 00 0f 84 9c 01 00 00 <44> 85 73 10 74 ea
>       44 8b 6b 14 41 f6 c5 01 75 d4 41 f6 c5 02 74 0f
> RSP: 0018:ff71570009e07a80 EFLAGS: 00010207
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000200
> RDX: ffffffffad8dc7c0 RSI: 0000000024924925 RDI: ff3e27850dea2000
> RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffffabfce739
> R10: ff3e27810cc42400 R11: 0000000000000000 R12: ff3e2781825ef970
> R13: 00000000ff3e2785 R14: 000000000000000c R15: 0000000000000001
> FS:  00007f5195b51740(0000)
> GS:ff3e278b12d40000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000010 CR3: 0000000626d24002 CR4: 0000000000361ee0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  ima_get_action+0x22/0x30
>  process_measurement+0xb0/0x830
>  ? page_add_file_rmap+0x15/0x170
>  ? alloc_set_pte+0x269/0x4c0
>  ? prep_new_page+0x81/0x140
>  ? simple_xattr_get+0x75/0xa0
>  ? selinux_file_open+0x9d/0xf0
>  ima_file_check+0x64/0x90
>  path_openat+0x571/0x1720
>  do_filp_open+0x9b/0x110
>  ? page_counter_try_charge+0x57/0xc0
>  ? files_cgroup_alloc_fd+0x38/0x60
>  ? __alloc_fd+0xd4/0x250
>  ? do_sys_open+0x1bd/0x250
>  do_sys_open+0x1bd/0x250
>  do_syscall_64+0x5d/0x1d0
>  entry_SYSCALL_64_after_hwframe+0x65/0xca
> 
> Commit c7423dbdbc9e ("ima: Handle -ESTALE returned by
> ima_filter_rule_match()") introduced call to ima_lsm_copy_rule within a
> RCU read-side critical section which contains kmalloc with GFP_KERNEL.
> This implies a possible sleep and violates limitations of RCU read-side
> critical sections on non-PREEMPT systems.
> 
> Sleeping within RCU read-side critical section might cause
> synchronize_rcu() returning early and break RCU protection, allowing a
> UAF to happen.
> 
> The root cause of this issue could be described as follows:
> > 	Thread A	|	Thread B	|
> > 			|ima_match_policy	|
> > 			|  rcu_read_lock	|
> > ima_lsm_update_rule	|			|
> >  synchronize_rcu	|			|
> > 			|    kmalloc(GFP_KERNEL)|
> > 			|      sleep		|
> ==> synchronize_rcu returns early
> >  kfree(entry)		|			|
> > 			|    entry = entry->next|
> ==> UAF happens and entry now becomes NULL (or could be anything).
> > 			|    entry->action	|
> ==> Accessing entry might cause panic.
> 
> To fix this issue, we are converting all kmalloc that is called within
> RCU read-side critical section to use GFP_ATOMIC.
> 
> Fixes: c7423dbdbc9e ("ima: Handle -ESTALE returned by ima_filter_rule_match()")
> Cc: stable@vger.kernel.org
> Signed-off-by: GUO Zihua <guozihua@huawei.com>
> Acked-by: John Johansen <john.johansen@canonical.com>
> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
> Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
> [PM: fixed missing comment, long lines, !CONFIG_IMA_LSM_RULES case]
> Signed-off-by: Paul Moore <paul@paul-moore.com>
> (cherry picked from commit 9a95c5bfbf02a0a7f5983280fe284a0ff0836c34)
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> ---
> Backporting notes:
> - Remove security_audit_rule_init() documentation changes
> - Add default return value parameter to call_int_hook()
>   in security_audit_rule_init()
> - Can be backported to 6.1.x, 5.15.x, 5.10.x

Thanks, Roberto.  I'll post a similar one for linux-6.8.y - linux-6.4.y.

Mimi

[PATCH] ima: Avoid blocking in RCU read-side critical section

[Mimi Zohar]

From: GUO Zihua <guozihua@huawei.com>

A panic happens in ima_match_policy:

BUG: unable to handle kernel NULL pointer dereference at 0000000000000010
PGD 42f873067 P4D 0
Oops: 0000 [#1] SMP NOPTI
CPU: 5 PID: 1286325 Comm: kubeletmonit.sh
Kdump: loaded Tainted: P
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
               BIOS 0.0.0 02/06/2015
RIP: 0010:ima_match_policy+0x84/0x450
Code: 49 89 fc 41 89 cf 31 ed 89 44 24 14 eb 1c 44 39
      7b 18 74 26 41 83 ff 05 74 20 48 8b 1b 48 3b 1d
      f2 b9 f4 00 0f 84 9c 01 00 00 <44> 85 73 10 74 ea
      44 8b 6b 14 41 f6 c5 01 75 d4 41 f6 c5 02 74 0f
RSP: 0018:ff71570009e07a80 EFLAGS: 00010207
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000200
RDX: ffffffffad8dc7c0 RSI: 0000000024924925 RDI: ff3e27850dea2000
RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffffabfce739
R10: ff3e27810cc42400 R11: 0000000000000000 R12: ff3e2781825ef970
R13: 00000000ff3e2785 R14: 000000000000000c R15: 0000000000000001
FS:  00007f5195b51740(0000)
GS:ff3e278b12d40000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000010 CR3: 0000000626d24002 CR4: 0000000000361ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 ima_get_action+0x22/0x30
 process_measurement+0xb0/0x830
 ? page_add_file_rmap+0x15/0x170
 ? alloc_set_pte+0x269/0x4c0
 ? prep_new_page+0x81/0x140
 ? simple_xattr_get+0x75/0xa0
 ? selinux_file_open+0x9d/0xf0
 ima_file_check+0x64/0x90
 path_openat+0x571/0x1720
 do_filp_open+0x9b/0x110
 ? page_counter_try_charge+0x57/0xc0
 ? files_cgroup_alloc_fd+0x38/0x60
 ? __alloc_fd+0xd4/0x250
 ? do_sys_open+0x1bd/0x250
 do_sys_open+0x1bd/0x250
 do_syscall_64+0x5d/0x1d0
 entry_SYSCALL_64_after_hwframe+0x65/0xca

Commit c7423dbdbc9e ("ima: Handle -ESTALE returned by
ima_filter_rule_match()") introduced call to ima_lsm_copy_rule within a
RCU read-side critical section which contains kmalloc with GFP_KERNEL.
This implies a possible sleep and violates limitations of RCU read-side
critical sections on non-PREEMPT systems.

Sleeping within RCU read-side critical section might cause
synchronize_rcu() returning early and break RCU protection, allowing a
UAF to happen.

The root cause of this issue could be described as follows:
|	Thread A	|	Thread B	|
|			|ima_match_policy	|
|			|  rcu_read_lock	|
|ima_lsm_update_rule	|			|
|  synchronize_rcu	|			|
|			|    kmalloc(GFP_KERNEL)|
|			|      sleep		|
==> synchronize_rcu returns early
|  kfree(entry)		|			|
|			|    entry = entry->next|
==> UAF happens and entry now becomes NULL (or could be anything).
|			|    entry->action	|
==> Accessing entry might cause panic.

To fix this issue, we are converting all kmalloc that is called within
RCU read-side critical section to use GFP_ATOMIC.

Fixes: c7423dbdbc9e ("ima: Handle -ESTALE returned by ima_filter_rule_match()")
Cc: stable@vger.kernel.org
Signed-off-by: GUO Zihua <guozihua@huawei.com>
Acked-by: John Johansen <john.johansen@canonical.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
[PM: fixed missing comment, long lines, !CONFIG_IMA_LSM_RULES case]
Signed-off-by: Paul Moore <paul@paul-moore.com>
(cherry picked from commit 9a95c5bfbf02a0a7f5983280fe284a0ff0836c34)
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
---
Backport notes:
- Restore default return value parameter to call_int_hook() in
security_audit_rule_init() in lieu of backporting commit 260017f31a8c
("lsm: use default hook return value in call_int_hook()").
- Applies to linux-6.8.y -> linux-6.4.y

 include/linux/lsm_hook_defs.h       |  2 +-
 include/linux/security.h            |  5 +++--
 kernel/auditfilter.c                |  5 +++--
 security/apparmor/audit.c           |  6 +++---
 security/apparmor/include/audit.h   |  2 +-
 security/integrity/ima/ima.h        |  2 +-
 security/integrity/ima/ima_policy.c | 15 +++++++++------
 security/security.c                 |  6 ++++--
 security/selinux/include/audit.h    |  4 +++-
 security/selinux/ss/services.c      |  5 +++--
 security/smack/smack_lsm.c          |  4 +++-
 11 files changed, 34 insertions(+), 22 deletions(-)

diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index f9b5baf1b5f4..4903a724e344 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -394,7 +394,7 @@ LSM_HOOK(int, 0, key_getsecurity, struct key *key, char **buffer)
 
 #ifdef CONFIG_AUDIT
 LSM_HOOK(int, 0, audit_rule_init, u32 field, u32 op, char *rulestr,
-	 void **lsmrule)
+	 void **lsmrule, gfp_t gfp)
 LSM_HOOK(int, 0, audit_rule_known, struct audit_krule *krule)
 LSM_HOOK(int, 0, audit_rule_match, u32 secid, u32 field, u32 op, void *lsmrule)
 LSM_HOOK(void, LSM_RET_VOID, audit_rule_free, void *lsmrule)
diff --git a/include/linux/security.h b/include/linux/security.h
index 3180d823e023..3f23438a0a4d 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1988,7 +1988,8 @@ static inline int security_key_getsecurity(struct key *key, char **_buffer)
 
 #ifdef CONFIG_AUDIT
 #ifdef CONFIG_SECURITY
-int security_audit_rule_init(u32 field, u32 op, char *rulestr, void **lsmrule);
+int security_audit_rule_init(u32 field, u32 op, char *rulestr, void **lsmrule,
+			     gfp_t gfp);
 int security_audit_rule_known(struct audit_krule *krule);
 int security_audit_rule_match(u32 secid, u32 field, u32 op, void *lsmrule);
 void security_audit_rule_free(void *lsmrule);
@@ -1996,7 +1997,7 @@ void security_audit_rule_free(void *lsmrule);
 #else
 
 static inline int security_audit_rule_init(u32 field, u32 op, char *rulestr,
-					   void **lsmrule)
+					   void **lsmrule, gfp_t gfp)
 {
 	return 0;
 }
diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
index 8317a37dea0b..685bccb20b6f 100644
--- a/kernel/auditfilter.c
+++ b/kernel/auditfilter.c
@@ -529,7 +529,8 @@ static struct audit_entry *audit_data_to_entry(struct audit_rule_data *data,
 			entry->rule.buflen += f_val;
 			f->lsm_str = str;
 			err = security_audit_rule_init(f->type, f->op, str,
-						       (void **)&f->lsm_rule);
+						       (void **)&f->lsm_rule,
+						       GFP_KERNEL);
 			/* Keep currently invalid fields around in case they
 			 * become valid after a policy reload. */
 			if (err == -EINVAL) {
@@ -799,7 +800,7 @@ static inline int audit_dupe_lsm_field(struct audit_field *df,
 
 	/* our own (refreshed) copy of lsm_rule */
 	ret = security_audit_rule_init(df->type, df->op, df->lsm_str,
-				       (void **)&df->lsm_rule);
+				       (void **)&df->lsm_rule, GFP_KERNEL);
 	/* Keep currently invalid fields around in case they
 	 * become valid after a policy reload. */
 	if (ret == -EINVAL) {
diff --git a/security/apparmor/audit.c b/security/apparmor/audit.c
index 45beb1c5f747..6b5181c668b5 100644
--- a/security/apparmor/audit.c
+++ b/security/apparmor/audit.c
@@ -217,7 +217,7 @@ void aa_audit_rule_free(void *vrule)
 	}
 }
 
-int aa_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule)
+int aa_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule, gfp_t gfp)
 {
 	struct aa_audit_rule *rule;
 
@@ -230,14 +230,14 @@ int aa_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule)
 		return -EINVAL;
 	}
 
-	rule = kzalloc(sizeof(struct aa_audit_rule), GFP_KERNEL);
+	rule = kzalloc(sizeof(struct aa_audit_rule), gfp);
 
 	if (!rule)
 		return -ENOMEM;
 
 	/* Currently rules are treated as coming from the root ns */
 	rule->label = aa_label_parse(&root_ns->unconfined->label, rulestr,
-				     GFP_KERNEL, true, false);
+				     gfp, true, false);
 	if (IS_ERR(rule->label)) {
 		int err = PTR_ERR(rule->label);
 		aa_audit_rule_free(rule);
diff --git a/security/apparmor/include/audit.h b/security/apparmor/include/audit.h
index acbb03b9bd25..0c8cc86b417b 100644
--- a/security/apparmor/include/audit.h
+++ b/security/apparmor/include/audit.h
@@ -200,7 +200,7 @@ static inline int complain_error(int error)
 }
 
 void aa_audit_rule_free(void *vrule);
-int aa_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule);
+int aa_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule, gfp_t gfp);
 int aa_audit_rule_known(struct audit_krule *rule);
 int aa_audit_rule_match(u32 sid, u32 field, u32 op, void *vrule);
 
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index c29db699c996..07a4586e129c 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -430,7 +430,7 @@ static inline void ima_free_modsig(struct modsig *modsig)
 #else
 
 static inline int ima_filter_rule_init(u32 field, u32 op, char *rulestr,
-				       void **lsmrule)
+				       void **lsmrule, gfp_t gfp)
 {
 	return -EINVAL;
 }
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index f69062617754..f3f46c6186c0 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -401,7 +401,8 @@ static void ima_free_rule(struct ima_rule_entry *entry)
 	kfree(entry);
 }
 
-static struct ima_rule_entry *ima_lsm_copy_rule(struct ima_rule_entry *entry)
+static struct ima_rule_entry *ima_lsm_copy_rule(struct ima_rule_entry *entry,
+						gfp_t gfp)
 {
 	struct ima_rule_entry *nentry;
 	int i;
@@ -410,7 +411,7 @@ static struct ima_rule_entry *ima_lsm_copy_rule(struct ima_rule_entry *entry)
 	 * Immutable elements are copied over as pointers and data; only
 	 * lsm rules can change
 	 */
-	nentry = kmemdup(entry, sizeof(*nentry), GFP_KERNEL);
+	nentry = kmemdup(entry, sizeof(*nentry), gfp);
 	if (!nentry)
 		return NULL;
 
@@ -425,7 +426,8 @@ static struct ima_rule_entry *ima_lsm_copy_rule(struct ima_rule_entry *entry)
 
 		ima_filter_rule_init(nentry->lsm[i].type, Audit_equal,
 				     nentry->lsm[i].args_p,
-				     &nentry->lsm[i].rule);
+				     &nentry->lsm[i].rule,
+				     gfp);
 		if (!nentry->lsm[i].rule)
 			pr_warn("rule for LSM \'%s\' is undefined\n",
 				nentry->lsm[i].args_p);
@@ -438,7 +440,7 @@ static int ima_lsm_update_rule(struct ima_rule_entry *entry)
 	int i;
 	struct ima_rule_entry *nentry;
 
-	nentry = ima_lsm_copy_rule(entry);
+	nentry = ima_lsm_copy_rule(entry, GFP_KERNEL);
 	if (!nentry)
 		return -ENOMEM;
 
@@ -664,7 +666,7 @@ static bool ima_match_rules(struct ima_rule_entry *rule,
 		}
 
 		if (rc == -ESTALE && !rule_reinitialized) {
-			lsm_rule = ima_lsm_copy_rule(rule);
+			lsm_rule = ima_lsm_copy_rule(rule, GFP_ATOMIC);
 			if (lsm_rule) {
 				rule_reinitialized = true;
 				goto retry;
@@ -1140,7 +1142,8 @@ static int ima_lsm_rule_init(struct ima_rule_entry *entry,
 	entry->lsm[lsm_rule].type = audit_type;
 	result = ima_filter_rule_init(entry->lsm[lsm_rule].type, Audit_equal,
 				      entry->lsm[lsm_rule].args_p,
-				      &entry->lsm[lsm_rule].rule);
+				      &entry->lsm[lsm_rule].rule,
+				      GFP_KERNEL);
 	if (!entry->lsm[lsm_rule].rule) {
 		pr_warn("rule for LSM \'%s\' is undefined\n",
 			entry->lsm[lsm_rule].args_p);
diff --git a/security/security.c b/security/security.c
index a344b8fa5530..e0ef2ac7600f 100644
--- a/security/security.c
+++ b/security/security.c
@@ -5350,15 +5350,17 @@ int security_key_getsecurity(struct key *key, char **buffer)
  * @op: rule operator
  * @rulestr: rule context
  * @lsmrule: receive buffer for audit rule struct
+ * @gfp: GFP flag used for kmalloc
  *
  * Allocate and initialize an LSM audit rule structure.
  *
  * Return: Return 0 if @lsmrule has been successfully set, -EINVAL in case of
  *         an invalid rule.
  */
-int security_audit_rule_init(u32 field, u32 op, char *rulestr, void **lsmrule)
+int security_audit_rule_init(u32 field, u32 op, char *rulestr, void **lsmrule,
+			     gfp_t gfp)
 {
-	return call_int_hook(audit_rule_init, 0, field, op, rulestr, lsmrule);
+	return call_int_hook(audit_rule_init, 0, field, op, rulestr, lsmrule, gfp);
 }
 
 /**
diff --git a/security/selinux/include/audit.h b/security/selinux/include/audit.h
index 52aca71210b4..29c7d4c86f6d 100644
--- a/security/selinux/include/audit.h
+++ b/security/selinux/include/audit.h
@@ -21,12 +21,14 @@
  *	@op: the operator the rule uses
  *	@rulestr: the text "target" of the rule
  *	@rule: pointer to the new rule structure returned via this
+ *	@gfp: GFP flag used for kmalloc
  *
  *	Returns 0 if successful, -errno if not.  On success, the rule structure
  *	will be allocated internally.  The caller must free this structure with
  *	selinux_audit_rule_free() after use.
  */
-int selinux_audit_rule_init(u32 field, u32 op, char *rulestr, void **rule);
+int selinux_audit_rule_init(u32 field, u32 op, char *rulestr, void **rule,
+			    gfp_t gfp);
 
 /**
  *	selinux_audit_rule_free - free an selinux audit rule structure.
diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index e88b1b6c4adb..ded250e525e9 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -3508,7 +3508,8 @@ void selinux_audit_rule_free(void *vrule)
 	}
 }
 
-int selinux_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule)
+int selinux_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule,
+			    gfp_t gfp)
 {
 	struct selinux_state *state = &selinux_state;
 	struct selinux_policy *policy;
@@ -3549,7 +3550,7 @@ int selinux_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule)
 		return -EINVAL;
 	}
 
-	tmprule = kzalloc(sizeof(struct selinux_audit_rule), GFP_KERNEL);
+	tmprule = kzalloc(sizeof(struct selinux_audit_rule), gfp);
 	if (!tmprule)
 		return -ENOMEM;
 	context_init(&tmprule->au_ctxt);
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 6f9a80783a5a..8cc3a6764379 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -4690,11 +4690,13 @@ static int smack_post_notification(const struct cred *w_cred,
  * @op: required testing operator (=, !=, >, <, ...)
  * @rulestr: smack label to be audited
  * @vrule: pointer to save our own audit rule representation
+ * @gfp: type of the memory for the allocation
  *
  * Prepare to audit cases where (@field @op @rulestr) is true.
  * The label to be audited is created if necessay.
  */
-static int smack_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule)
+static int smack_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule,
+				 gfp_t gfp)
 {
 	struct smack_known *skp;
 	char **rule = (char **)vrule;
-- 
2.43.0

Re: [PATCH] ima: Avoid blocking in RCU read-side critical section

[Greg KH]

On Sun, Jul 07, 2024 at 08:04:39AM -0400, Mimi Zohar wrote:
> From: GUO Zihua <guozihua@huawei.com>
> 
> A panic happens in ima_match_policy:
> 
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000010
> PGD 42f873067 P4D 0
> Oops: 0000 [#1] SMP NOPTI
> CPU: 5 PID: 1286325 Comm: kubeletmonit.sh
> Kdump: loaded Tainted: P
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
>                BIOS 0.0.0 02/06/2015
> RIP: 0010:ima_match_policy+0x84/0x450
> Code: 49 89 fc 41 89 cf 31 ed 89 44 24 14 eb 1c 44 39
>       7b 18 74 26 41 83 ff 05 74 20 48 8b 1b 48 3b 1d
>       f2 b9 f4 00 0f 84 9c 01 00 00 <44> 85 73 10 74 ea
>       44 8b 6b 14 41 f6 c5 01 75 d4 41 f6 c5 02 74 0f
> RSP: 0018:ff71570009e07a80 EFLAGS: 00010207
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000200
> RDX: ffffffffad8dc7c0 RSI: 0000000024924925 RDI: ff3e27850dea2000
> RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffffabfce739
> R10: ff3e27810cc42400 R11: 0000000000000000 R12: ff3e2781825ef970
> R13: 00000000ff3e2785 R14: 000000000000000c R15: 0000000000000001
> FS:  00007f5195b51740(0000)
> GS:ff3e278b12d40000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000010 CR3: 0000000626d24002 CR4: 0000000000361ee0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  ima_get_action+0x22/0x30
>  process_measurement+0xb0/0x830
>  ? page_add_file_rmap+0x15/0x170
>  ? alloc_set_pte+0x269/0x4c0
>  ? prep_new_page+0x81/0x140
>  ? simple_xattr_get+0x75/0xa0
>  ? selinux_file_open+0x9d/0xf0
>  ima_file_check+0x64/0x90
>  path_openat+0x571/0x1720
>  do_filp_open+0x9b/0x110
>  ? page_counter_try_charge+0x57/0xc0
>  ? files_cgroup_alloc_fd+0x38/0x60
>  ? __alloc_fd+0xd4/0x250
>  ? do_sys_open+0x1bd/0x250
>  do_sys_open+0x1bd/0x250
>  do_syscall_64+0x5d/0x1d0
>  entry_SYSCALL_64_after_hwframe+0x65/0xca
> 
> Commit c7423dbdbc9e ("ima: Handle -ESTALE returned by
> ima_filter_rule_match()") introduced call to ima_lsm_copy_rule within a
> RCU read-side critical section which contains kmalloc with GFP_KERNEL.
> This implies a possible sleep and violates limitations of RCU read-side
> critical sections on non-PREEMPT systems.
> 
> Sleeping within RCU read-side critical section might cause
> synchronize_rcu() returning early and break RCU protection, allowing a
> UAF to happen.
> 
> The root cause of this issue could be described as follows:
> |	Thread A	|	Thread B	|
> |			|ima_match_policy	|
> |			|  rcu_read_lock	|
> |ima_lsm_update_rule	|			|
> |  synchronize_rcu	|			|
> |			|    kmalloc(GFP_KERNEL)|
> |			|      sleep		|
> ==> synchronize_rcu returns early
> |  kfree(entry)		|			|
> |			|    entry = entry->next|
> ==> UAF happens and entry now becomes NULL (or could be anything).
> |			|    entry->action	|
> ==> Accessing entry might cause panic.
> 
> To fix this issue, we are converting all kmalloc that is called within
> RCU read-side critical section to use GFP_ATOMIC.
> 
> Fixes: c7423dbdbc9e ("ima: Handle -ESTALE returned by ima_filter_rule_match()")
> Cc: stable@vger.kernel.org
> Signed-off-by: GUO Zihua <guozihua@huawei.com>
> Acked-by: John Johansen <john.johansen@canonical.com>
> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
> Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
> [PM: fixed missing comment, long lines, !CONFIG_IMA_LSM_RULES case]
> Signed-off-by: Paul Moore <paul@paul-moore.com>
> (cherry picked from commit 9a95c5bfbf02a0a7f5983280fe284a0ff0836c34)
> Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
> ---
> Backport notes:
> - Restore default return value parameter to call_int_hook() in
> security_audit_rule_init() in lieu of backporting commit 260017f31a8c
> ("lsm: use default hook return value in call_int_hook()").
> - Applies to linux-6.8.y -> linux-6.4.y

Now applied to 6.6.y, thanks.

greg k-h

Re: [PATCH] ima: Avoid blocking in RCU read-side critical section

[Greg KH]

On Thu, Jul 04, 2024 at 12:43:03PM +0200, Roberto Sassu wrote:
> From: GUO Zihua <guozihua@huawei.com>
> 
> A panic happens in ima_match_policy:
> 
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000010
> PGD 42f873067 P4D 0
> Oops: 0000 [#1] SMP NOPTI
> CPU: 5 PID: 1286325 Comm: kubeletmonit.sh
> Kdump: loaded Tainted: P
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
>                BIOS 0.0.0 02/06/2015
> RIP: 0010:ima_match_policy+0x84/0x450
> Code: 49 89 fc 41 89 cf 31 ed 89 44 24 14 eb 1c 44 39
>       7b 18 74 26 41 83 ff 05 74 20 48 8b 1b 48 3b 1d
>       f2 b9 f4 00 0f 84 9c 01 00 00 <44> 85 73 10 74 ea
>       44 8b 6b 14 41 f6 c5 01 75 d4 41 f6 c5 02 74 0f
> RSP: 0018:ff71570009e07a80 EFLAGS: 00010207
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000200
> RDX: ffffffffad8dc7c0 RSI: 0000000024924925 RDI: ff3e27850dea2000
> RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffffabfce739
> R10: ff3e27810cc42400 R11: 0000000000000000 R12: ff3e2781825ef970
> R13: 00000000ff3e2785 R14: 000000000000000c R15: 0000000000000001
> FS:  00007f5195b51740(0000)
> GS:ff3e278b12d40000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000010 CR3: 0000000626d24002 CR4: 0000000000361ee0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  ima_get_action+0x22/0x30
>  process_measurement+0xb0/0x830
>  ? page_add_file_rmap+0x15/0x170
>  ? alloc_set_pte+0x269/0x4c0
>  ? prep_new_page+0x81/0x140
>  ? simple_xattr_get+0x75/0xa0
>  ? selinux_file_open+0x9d/0xf0
>  ima_file_check+0x64/0x90
>  path_openat+0x571/0x1720
>  do_filp_open+0x9b/0x110
>  ? page_counter_try_charge+0x57/0xc0
>  ? files_cgroup_alloc_fd+0x38/0x60
>  ? __alloc_fd+0xd4/0x250
>  ? do_sys_open+0x1bd/0x250
>  do_sys_open+0x1bd/0x250
>  do_syscall_64+0x5d/0x1d0
>  entry_SYSCALL_64_after_hwframe+0x65/0xca
> 
> Commit c7423dbdbc9e ("ima: Handle -ESTALE returned by
> ima_filter_rule_match()") introduced call to ima_lsm_copy_rule within a
> RCU read-side critical section which contains kmalloc with GFP_KERNEL.
> This implies a possible sleep and violates limitations of RCU read-side
> critical sections on non-PREEMPT systems.
> 
> Sleeping within RCU read-side critical section might cause
> synchronize_rcu() returning early and break RCU protection, allowing a
> UAF to happen.
> 
> The root cause of this issue could be described as follows:
> |	Thread A	|	Thread B	|
> |			|ima_match_policy	|
> |			|  rcu_read_lock	|
> |ima_lsm_update_rule	|			|
> |  synchronize_rcu	|			|
> |			|    kmalloc(GFP_KERNEL)|
> |			|      sleep		|
> ==> synchronize_rcu returns early
> |  kfree(entry)		|			|
> |			|    entry = entry->next|
> ==> UAF happens and entry now becomes NULL (or could be anything).
> |			|    entry->action	|
> ==> Accessing entry might cause panic.
> 
> To fix this issue, we are converting all kmalloc that is called within
> RCU read-side critical section to use GFP_ATOMIC.
> 
> Fixes: c7423dbdbc9e ("ima: Handle -ESTALE returned by ima_filter_rule_match()")
> Cc: stable@vger.kernel.org
> Signed-off-by: GUO Zihua <guozihua@huawei.com>
> Acked-by: John Johansen <john.johansen@canonical.com>
> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
> Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
> [PM: fixed missing comment, long lines, !CONFIG_IMA_LSM_RULES case]
> Signed-off-by: Paul Moore <paul@paul-moore.com>
> (cherry picked from commit 9a95c5bfbf02a0a7f5983280fe284a0ff0836c34)
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> ---
> Backporting notes:
> - Remove security_audit_rule_init() documentation changes
> - Add default return value parameter to call_int_hook()
>   in security_audit_rule_init()
> - Can be backported to 6.1.x, 5.15.x, 5.10.x

Now queued up, thanks.

greg k-h