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List:       git-commits-head
Subject:    PKCS#7: pkcs7_validate_trust(): initialize the _trusted output argument
From:       "Linux Kernel Mailing List" <linux-kernel () vger ! kernel ! org>
Date:       2016-03-30 18:31:30
Message-ID: 20160330183130.76790660F2F () gitolite ! kernel ! org
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Web:        https://git.kernel.org/torvalds/c/e54358915d0a00399c11c2c23ae1be674cba188a
Commit:     e54358915d0a00399c11c2c23ae1be674cba188a
Parent:     dfe97ad30e8c038261663a18b9e04b8b5bc07bea
Refname:    refs/heads/master
Author:     Nicolai Stange <nicstange@gmail.com>
AuthorDate: Sun Mar 20 23:23:46 2016 +0100
Committer:  Herbert Xu <herbert@gondor.apana.org.au>
CommitDate: Wed Mar 23 20:57:24 2016 +0800

    PKCS#7: pkcs7_validate_trust(): initialize the _trusted output argument
    
    Despite what the DocBook comment to pkcs7_validate_trust() says, the
    *_trusted argument is never set to false.
    
    pkcs7_validate_trust() only positively sets *_trusted upon encountering
    a trusted PKCS#7 SignedInfo block.
    
    This is quite unfortunate since its callers, system_verify_data() for
    example, depend on pkcs7_validate_trust() clearing *_trusted on non-trust.
    
    Indeed, UBSAN splats when attempting to load the uninitialized local
    variable 'trusted' from system_verify_data() in pkcs7_validate_trust():
    
      UBSAN: Undefined behaviour in crypto/asymmetric_keys/pkcs7_trust.c:194:14
      load of value 82 is not a valid value for type '_Bool'
      [...]
      Call Trace:
        [<ffffffff818c4d35>] dump_stack+0xbc/0x117
        [<ffffffff818c4c79>] ? _atomic_dec_and_lock+0x169/0x169
        [<ffffffff8194113b>] ubsan_epilogue+0xd/0x4e
        [<ffffffff819419fa>] __ubsan_handle_load_invalid_value+0x111/0x158
        [<ffffffff819418e9>] ? val_to_string.constprop.12+0xcf/0xcf
        [<ffffffff818334a4>] ? x509_request_asymmetric_key+0x114/0x370
        [<ffffffff814b83f0>] ? kfree+0x220/0x370
        [<ffffffff818312c2>] ? public_key_verify_signature_2+0x32/0x50
        [<ffffffff81835e04>] pkcs7_validate_trust+0x524/0x5f0
        [<ffffffff813c391a>] system_verify_data+0xca/0x170
        [<ffffffff813c3850>] ? top_trace_array+0x9b/0x9b
        [<ffffffff81510b29>] ? __vfs_read+0x279/0x3d0
        [<ffffffff8129372f>] mod_verify_sig+0x1ff/0x290
        [...]
    
    The implication is that pkcs7_validate_trust() effectively grants trust
    when it really shouldn't have.
    
    Fix this by explicitly setting *_trusted to false at the very beginning
    of pkcs7_validate_trust().
    
    Cc: <stable@vger.kernel.org>
    Signed-off-by: Nicolai Stange <nicstange@gmail.com>
    Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---
 crypto/asymmetric_keys/pkcs7_trust.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/crypto/asymmetric_keys/pkcs7_trust.c b/crypto/asymmetric_keys/pkcs7_trust.c
index 90d6d47..ecdb5a2 100644
--- a/crypto/asymmetric_keys/pkcs7_trust.c
+++ b/crypto/asymmetric_keys/pkcs7_trust.c
@@ -178,6 +178,8 @@ int pkcs7_validate_trust(struct pkcs7_message *pkcs7,
 	int cached_ret = -ENOKEY;
 	int ret;
 
+	*_trusted = false;
+
 	for (p = pkcs7->certs; p; p = p->next)
 		p->seen = false;
 
--
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