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![Tyler Hicks](/assets/img/avatar_default.png)
Use the shash interface, rather than the hash interface, when hashing AppArmor profiles. The shash interface does not use scatterlists and it is a better fit for what AppArmor needs. This fixes a kernel paging BUG when aa_calc_profile_hash() is passed a buffer from vmalloc(). The hash interface requires callers to handle vmalloc() buffers differently than what AppArmor was doing. Due to vmalloc() memory not being physically contiguous, each individual page behind the buffer must be assigned to a scatterlist with sg_set_page() and then the scatterlist passed to crypto_hash_update(). The shash interface does not have that limitation and allows vmalloc() and kmalloc() buffers to be handled in the same manner. BugLink: https://launchpad.net/bugs/1216294/ BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=62261 Signed-off-by: Tyler Hicks <tyhicks@canonical.com> Acked-by: Seth Arnold <seth.arnold@canonical.com> Signed-off-by: John Johansen <john.johansen@canonical.com> Signed-off-by: James Morris <james.l.morris@oracle.com>
95 lines
2.1 KiB
C
95 lines
2.1 KiB
C
/*
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* AppArmor security module
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*
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* This file contains AppArmor policy loading interface function definitions.
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*
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* Copyright 2013 Canonical Ltd.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation, version 2 of the
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* License.
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*
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* Fns to provide a checksum of policy that has been loaded this can be
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* compared to userspace policy compiles to check loaded policy is what
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* it should be.
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*/
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#include <crypto/hash.h>
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#include "include/apparmor.h"
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#include "include/crypto.h"
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static unsigned int apparmor_hash_size;
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static struct crypto_shash *apparmor_tfm;
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unsigned int aa_hash_size(void)
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{
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return apparmor_hash_size;
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}
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int aa_calc_profile_hash(struct aa_profile *profile, u32 version, void *start,
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size_t len)
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{
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struct {
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struct shash_desc shash;
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char ctx[crypto_shash_descsize(apparmor_tfm)];
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} desc;
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int error = -ENOMEM;
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u32 le32_version = cpu_to_le32(version);
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if (!apparmor_tfm)
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return 0;
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profile->hash = kzalloc(apparmor_hash_size, GFP_KERNEL);
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if (!profile->hash)
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goto fail;
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desc.shash.tfm = apparmor_tfm;
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desc.shash.flags = 0;
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error = crypto_shash_init(&desc.shash);
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if (error)
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goto fail;
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error = crypto_shash_update(&desc.shash, (u8 *) &le32_version, 4);
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if (error)
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goto fail;
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error = crypto_shash_update(&desc.shash, (u8 *) start, len);
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if (error)
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goto fail;
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error = crypto_shash_final(&desc.shash, profile->hash);
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if (error)
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goto fail;
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return 0;
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fail:
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kfree(profile->hash);
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profile->hash = NULL;
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return error;
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}
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static int __init init_profile_hash(void)
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{
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struct crypto_shash *tfm;
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if (!apparmor_initialized)
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return 0;
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tfm = crypto_alloc_shash("sha1", 0, CRYPTO_ALG_ASYNC);
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if (IS_ERR(tfm)) {
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int error = PTR_ERR(tfm);
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AA_ERROR("failed to setup profile sha1 hashing: %d\n", error);
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return error;
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}
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apparmor_tfm = tfm;
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apparmor_hash_size = crypto_shash_digestsize(apparmor_tfm);
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aa_info_message("AppArmor sha1 policy hashing enabled");
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return 0;
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}
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late_initcall(init_profile_hash);
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