[PATCH 5.5 085/176] audit: fix error handling in audit_data_to_entry()

Greg Kroah-Hartman
2020-03-03T17:47:57Z

From: Paul Moore <paul@paul-moore.com>

commit 2ad3e17ebf94b7b7f3f64c050ff168f9915345eb upstream.

Commit 219ca39427bf ("audit: use union for audit_field values since
they are mutually exclusive") combined a number of separate fields in
the audit_field struct into a single union. Generally this worked
just fine because they are generally mutually exclusive.
Unfortunately in audit_data_to_entry() the overlap can be a problem
when a specific error case is triggered that causes the error path
code to attempt to cleanup an audit_field struct and the cleanup
involves attempting to free a stored LSM string (the lsm_str field).
Currently the code always has a non-NULL value in the
audit_field.lsm_str field as the top of the for-loop transfers a
value into audit_field.val (both .lsm_str and .val are part of the
same union); if audit_data_to_entry() fails and the audit_field
struct is specified to contain a LSM string, but the
audit_field.lsm_str has not yet been properly set, the error handling
code will attempt to free the bogus audit_field.lsm_str value that
was set with audit_field.val at the top of the for-loop.

This patch corrects this by ensuring that the audit_field.val is only
set when needed (it is cleared when the audit_field struct is
allocated with kcalloc()). It also corrects a few other issues to
ensure that in case of error the proper error code is returned.

Cc: stable@vger.kernel.org
Fixes: 219ca39427bf ("audit: use union for audit_field values since they are mutually exclusive")
Reported-by: syzbot+1f4d90ead370d72e450b@syzkaller.appspotmail.com
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
kernel/auditfilter.c | 71 ++++++++++++++++++++++++++++-----------------------
1 file changed, 39 insertions(+), 32 deletions(-)

--- a/kernel/auditfilter.c
+++ b/kernel/auditfilter.c
@@ -456,6 +456,7 @@ static struct audit_entry *audit_data_to
bufp = data->buf;
for (i = 0; i < data->field_count; i++) {
struct audit_field *f = &entry->rule.fields[i];
+ u32 f_val;

err = -EINVAL;

@@ -464,12 +465,12 @@ static struct audit_entry *audit_data_to
goto exit_free;

f->type = data->fields[i];
- f->val = data->values[i];
+ f_val = data->values[i];

/* Support legacy tests for a valid loginuid */
- if ((f->type == AUDIT_LOGINUID) && (f->val == AUDIT_UID_UNSET)) {
+ if ((f->type == AUDIT_LOGINUID) && (f_val == AUDIT_UID_UNSET)) {
f->type = AUDIT_LOGINUID_SET;
- f->val = 0;
+ f_val = 0;
entry->rule.pflags |= AUDIT_LOGINUID_LEGACY;
}

@@ -485,7 +486,7 @@ static struct audit_entry *audit_data_to
case AUDIT_SUID:
case AUDIT_FSUID:
case AUDIT_OBJ_UID:
- f->uid = make_kuid(current_user_ns(), f->val);
+ f->uid = make_kuid(current_user_ns(), f_val);
if (!uid_valid(f->uid))
goto exit_free;
break;
@@ -494,11 +495,12 @@ static struct audit_entry *audit_data_to
case AUDIT_SGID:
case AUDIT_FSGID:
case AUDIT_OBJ_GID:
- f->gid = make_kgid(current_user_ns(), f->val);
+ f->gid = make_kgid(current_user_ns(), f_val);
if (!gid_valid(f->gid))
goto exit_free;
break;
case AUDIT_ARCH:
+ f->val = f_val;
entry->rule.arch_f = f;
break;
case AUDIT_SUBJ_USER:
@@ -511,11 +513,13 @@ static struct audit_entry *audit_data_to
case AUDIT_OBJ_TYPE:
case AUDIT_OBJ_LEV_LOW:
case AUDIT_OBJ_LEV_HIGH:
- str = audit_unpack_string(&bufp, &remain, f->val);
- if (IS_ERR(str))
+ str = audit_unpack_string(&bufp, &remain, f_val);
+ if (IS_ERR(str)) {
+ err = PTR_ERR(str);
goto exit_free;
- entry->rule.buflen += f->val;
-
+ }
+ entry->rule.buflen += f_val;
+ f->lsm_str = str;
err = security_audit_rule_init(f->type, f->op, str,
(void **)&f->lsm_rule);
/* Keep currently invalid fields around in case they
@@ -524,68 +528,71 @@ static struct audit_entry *audit_data_to
pr_warn("audit rule for LSM \'%s\' is invalid\n",
str);
err = 0;
- }
- if (err) {
- kfree(str);
+ } else if (err)
goto exit_free;
- } else
- f->lsm_str = str;
break;
case AUDIT_WATCH:
- str = audit_unpack_string(&bufp, &remain, f->val);
- if (IS_ERR(str))
+ str = audit_unpack_string(&bufp, &remain, f_val);
+ if (IS_ERR(str)) {
+ err = PTR_ERR(str);
goto exit_free;
- entry->rule.buflen += f->val;
-
- err = audit_to_watch(&entry->rule, str, f->val, f->op);
+ }
+ err = audit_to_watch(&entry->rule, str, f_val, f->op);
if (err) {
kfree(str);
goto exit_free;
}
+ entry->rule.buflen += f_val;
break;
case AUDIT_DIR:
- str = audit_unpack_string(&bufp, &remain, f->val);
- if (IS_ERR(str))
+ str = audit_unpack_string(&bufp, &remain, f_val);
+ if (IS_ERR(str)) {
+ err = PTR_ERR(str);
goto exit_free;
- entry->rule.buflen += f->val;
-
+ }
err = audit_make_tree(&entry->rule, str, f->op);
kfree(str);
if (err)
goto exit_free;
+ entry->rule.buflen += f_val;
break;
case AUDIT_INODE:
+ f->val = f_val;
err = audit_to_inode(&entry->rule, f);
if (err)
goto exit_free;
break;
case AUDIT_FILTERKEY:
- if (entry->rule.filterkey || f->val > AUDIT_MAX_KEY_LEN)
+ if (entry->rule.filterkey || f_val > AUDIT_MAX_KEY_LEN)
goto exit_free;
- str = audit_unpack_string(&bufp, &remain, f->val);
- if (IS_ERR(str))
+ str = audit_unpack_string(&bufp, &remain, f_val);
+ if (IS_ERR(str)) {
+ err = PTR_ERR(str);
goto exit_free;
- entry->rule.buflen += f->val;
+ }
+ entry->rule.buflen += f_val;
entry->rule.filterkey = str;
break;
case AUDIT_EXE:
- if (entry->rule.exe || f->val > PATH_MAX)
+ if (entry->rule.exe || f_val > PATH_MAX)
goto exit_free;
- str = audit_unpack_string(&bufp, &remain, f->val);
+ str = audit_unpack_string(&bufp, &remain, f_val);
if (IS_ERR(str)) {
err = PTR_ERR(str);
goto exit_free;
}
- entry->rule.buflen += f->val;
-
- audit_mark = audit_alloc_mark(&entry->rule, str, f->val);
+ audit_mark = audit_alloc_mark(&entry->rule, str, f_val);
if (IS_ERR(audit_mark)) {
kfree(str);
err = PTR_ERR(audit_mark);
goto exit_free;
}
+ entry->rule.buflen += f_val;
entry->rule.exe = audit_mark;
break;
+ default:
+ f->val = f_val;
+ break;
}
}