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    Subject[PATCH 4.4 081/101] ima: Directly assign the ima_default_policy pointer to ima_rules
    Date
    From: Roberto Sassu <roberto.sassu@huawei.com>

    [ Upstream commit 067a436b1b0aafa593344fddd711a755a58afb3b ]

    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>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    security/integrity/ima/ima_policy.c | 3 +--
    1 file changed, 1 insertion(+), 2 deletions(-)

    diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
    index 3997e206f82d..0ddc8cb6411b 100644
    --- a/security/integrity/ima/ima_policy.c
    +++ b/security/integrity/ima/ima_policy.c
    @@ -135,7 +135,7 @@ static struct ima_rule_entry default_appraise_rules[] = {

    static LIST_HEAD(ima_default_rules);
    static LIST_HEAD(ima_policy_rules);
    -static struct list_head *ima_rules;
    +static struct list_head *ima_rules = &ima_default_rules;

    static DEFINE_MUTEX(ima_rules_mutex);

    @@ -412,7 +412,6 @@ void __init ima_init_policy(void)
    &ima_default_rules);
    }

    - ima_rules = &ima_default_rules;
    }

    /**
    --
    2.25.1


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