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@xxxxxxxxxxxxxxx
Signed-off-by: GUO Zihua <guozihua@xxxxxxxxxx>
---
v2:
Changed the audit_rule_init security hook to accept a new GFP flag, as
per Stephen's suggestion.
---
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_policy.c | 8 +++++---
security/security.c | 6 ++++--
security/selinux/include/audit.h | 4 +++-
security/selinux/ss/services.c | 5 +++--
security/smack/smack_lsm.c | 3 ++-
10 files changed, 28 insertions(+), 18 deletions(-)
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 334e00efbde4..7e539f6f8c67 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -412,7 +412,7 @@ LSM_HOOK(void, LSM_RET_VOID, key_post_create_or_update, struct key *keyring,
#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 41a8f667bdfa..5122e3ad83b1 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -2048,7 +2048,8 @@ static inline void security_key_post_create_or_update(struct key *keyring,
#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);
@@ -2056,7 +2057,7 @@ 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 be8c680121e4..d6ef4f4f9cba 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_policy.c b/security/integrity/ima/ima_policy.c
index c0556907c2e6..216ffe388ce5 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -410,7 +410,7 @@ 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_ATOMIC);
if (!nentry)
return NULL;
@@ -425,7 +425,8 @@ 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_ATOMIC);
if (!nentry->lsm[i].rule)
pr_warn("rule for LSM \'%s\' is undefined\n",
nentry->lsm[i].args_p);
@@ -1140,7 +1141,8 @@ 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 0a9a0ac3f266..4fd3c839353e 100644
--- a/security/security.c
+++ b/security/security.c
@@ -5331,15 +5331,17 @@ void security_key_post_create_or_update(struct key *keyring, struct key *key,
* @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, field, op, rulestr, lsmrule);
+ return call_int_hook(audit_rule_init, 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 146667937811..a4943628d75a 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -4696,7 +4696,8 @@ static int smack_post_notification(const struct cred *w_cred,
* 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
