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ima: Avoid blocking in RCU read-side critical section

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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 c7423dbdbc ("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: c7423dbdbc ("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>
This commit is contained in:
GUO Zihua 2024-05-07 01:25:41 +00:00 committed by Paul Moore
parent 83a7eefedc
commit 9a95c5bfbf
11 changed files with 34 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/lsm_hook_defs.h
View File

@ -413,7 +413,7 @@ 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)

5
include/linux/security.h
View File

@ -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;
}

5
kernel/auditfilter.c
View File

@ -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) {

6
security/apparmor/audit.c
View File

@ -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);

2
security/apparmor/include/audit.h
View File

@ -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);

2
security/integrity/ima/ima.h
View File

@ -546,7 +546,7 @@ 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;
}

15
security/integrity/ima/ima_policy.c
View File

@ -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 @@ retry:
}
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);

6
security/security.c
View File

@ -5332,15 +5332,17 @@ 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);
}
/**

4
security/selinux/include/audit.h
View File

@ -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.

5
security/selinux/ss/services.c
View File

@ -3507,7 +3507,8 @@ 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;
@ -3548,7 +3549,7 @@ 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);

4
security/smack/smack_lsm.c
View File

@ -4693,11 +4693,13 @@ 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;