The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 067a436b1b0aafa593344fddd711a755a58afb3b Mon Sep 17 00:00:00 2001
From: Roberto Sassu roberto.sassu@huawei.com Date: Wed, 3 Jun 2020 17:08:20 +0200 Subject: [PATCH] ima: Directly assign the ima_default_policy pointer to ima_rules
This patch prevents the following oops:
[ 10.771813] BUG: kernel NULL pointer dereference, address: 0000000000000 [...] [ 10.779790] RIP: 0010:ima_match_policy+0xf7/0xb80 [...] [ 10.798576] Call Trace: [ 10.798993] ? ima_lsm_policy_change+0x2b0/0x2b0 [ 10.799753] ? inode_init_owner+0x1a0/0x1a0 [ 10.800484] ? _raw_spin_lock+0x7a/0xd0 [ 10.801592] ima_must_appraise.part.0+0xb6/0xf0 [ 10.802313] ? ima_fix_xattr.isra.0+0xd0/0xd0 [ 10.803167] ima_must_appraise+0x4f/0x70 [ 10.804004] ima_post_path_mknod+0x2e/0x80 [ 10.804800] do_mknodat+0x396/0x3c0
It occurs when there is a failure during IMA initialization, and ima_init_policy() is not called. IMA hooks still call ima_match_policy() but ima_rules is NULL. This patch prevents the crash by directly assigning the ima_default_policy pointer to ima_rules when ima_rules is defined. This wouldn't alter the existing behavior, as ima_rules is always set at the end of ima_init_policy().
Cc: stable@vger.kernel.org # 3.7.x Fixes: 07f6a79415d7d ("ima: add appraise action keywords and default rules") Reported-by: Takashi Iwai tiwai@suse.de Signed-off-by: Roberto Sassu roberto.sassu@huawei.com Signed-off-by: Mimi Zohar zohar@linux.ibm.com
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c index ef7f68cc935e..e493063a3c34 100644 --- a/security/integrity/ima/ima_policy.c +++ b/security/integrity/ima/ima_policy.c @@ -204,7 +204,7 @@ static struct ima_rule_entry *arch_policy_entry __ro_after_init; static LIST_HEAD(ima_default_rules); static LIST_HEAD(ima_policy_rules); static LIST_HEAD(ima_temp_rules); -static struct list_head *ima_rules; +static struct list_head *ima_rules = &ima_default_rules;
/* Pre-allocated buffer used for matching keyrings. */ static char *ima_keyrings; @@ -768,7 +768,6 @@ void __init ima_init_policy(void) ARRAY_SIZE(default_appraise_rules), IMA_DEFAULT_POLICY);
- ima_rules = &ima_default_rules; ima_update_policy_flag(); }