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SubjectRe: [PATCH 3/6] ima: Simplify policy_func_show.
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On Thu, 2017-04-20 at 17:40 -0300, Thiago Jung Bauermann wrote:
> Am Donnerstag, 20. April 2017, 08:13:23 BRT schrieb Mimi Zohar:
> > On Tue, 2017-04-18 at 17:17 -0300, Thiago Jung Bauermann wrote:
> > > If the func_tokens array uses the same indices as enum ima_hooks,
> > > policy_func_show can be a lot simpler, and the func_* enum becomes
> > > unnecessary.
> >
> > My main concern with separating the enumeration from the string
> > definition is that they might become out of sync. Perhaps using
> > macros, similar to those used for kernel_read_file_id_str(), would be
> > better?
>
> I agree that it would be better. Is the patch below what you had in mind?

Yes, I haven't tested it yet, but it looks right.
>
> I also noticed that policy_func_show can be even simpler if we stop using the
> printf format string from the policy_tokens table. What do you think?
>
> --
> Thiago Jung Bauermann
> IBM Linux Technology Center
>
>
> From 594628c94f5dd7c6d2624944a76b6a01f9668128 Mon Sep 17 00:00:00 2001
> From: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
> Date: Mon, 10 Apr 2017 14:59:44 -0300
> Subject: [PATCH 3/6] ima: Simplify policy_func_show.
>
> If the func_tokens array uses the same indices as enum ima_hooks,
> policy_func_show can be a lot simpler, and the func_* enum becomes
> unnecessary.
>
> Also, if we use the same macro trick used by kernel_read_file_id_str we can
> use one hooks list for both the enum and the string array, making sure they
> are always in sync (suggested by Mimi Zohar).

> Finally, by using the printf pattern for the function token directly
> instead of using the pt macro we can simplify policy_func_show even further
> and avoid the need of having a temporary buffer. Since the only use of
> Opt_func's printf pattern in policy_tokens was in policy_func_show, we
> don't need it at all anymore so remove it.
>
> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
> ---
> security/integrity/ima/ima.h | 25 +++++++++-------
> security/integrity/ima/ima_policy.c | 60 +++++--------------------------------
> 2 files changed, 22 insertions(+), 63 deletions(-)
>
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index b563fbd4d122..51ef805cf7f3 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -172,17 +172,22 @@ static inline unsigned long ima_hash_key(u8 *digest)
> return hash_long(*digest, IMA_HASH_BITS);
> }
>
> +#define __ima_hooks(hook) \
> + hook(NONE) \
> + hook(FILE_CHECK) \
> + hook(MMAP_CHECK) \
> + hook(BPRM_CHECK) \
> + hook(POST_SETATTR) \
> + hook(MODULE_CHECK) \
> + hook(FIRMWARE_CHECK) \
> + hook(KEXEC_KERNEL_CHECK) \
> + hook(KEXEC_INITRAMFS_CHECK) \
> + hook(POLICY_CHECK) \
> + hook(MAX_CHECK)
> +#define __ima_hook_enumify(ENUM) ENUM,
> +
> enum ima_hooks {
> - FILE_CHECK = 1,
> - MMAP_CHECK,
> - BPRM_CHECK,
> - POST_SETATTR,
> - MODULE_CHECK,
> - FIRMWARE_CHECK,
> - KEXEC_KERNEL_CHECK,
> - KEXEC_INITRAMFS_CHECK,
> - POLICY_CHECK,
> - MAX_CHECK
> + __ima_hooks(__ima_hook_enumify)
> };
>
> /* LIM API function definitions */
> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index cfda5d7b17ec..39d43a5beb5a 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -503,7 +503,7 @@ static match_table_t policy_tokens = {
> {Opt_subj_user, "subj_user=%s"},
> {Opt_subj_role, "subj_role=%s"},
> {Opt_subj_type, "subj_type=%s"},
> - {Opt_func, "func=%s"},
> + {Opt_func, NULL},
> {Opt_mask, "mask=%s"},
> {Opt_fsmagic, "fsmagic=%s"},
> {Opt_fsuuid, "fsuuid=%s"},
> @@ -896,23 +896,10 @@ static const char *const mask_tokens[] = {
> "MAY_APPEND"
> };
>
> -enum {
> - func_file = 0, func_mmap, func_bprm,
> - func_module, func_firmware, func_post,
> - func_kexec_kernel, func_kexec_initramfs,
> - func_policy
> -};
> +#define __ima_hook_stringify(str) #str,
>
> static const char *const func_tokens[] = {
> - "FILE_CHECK",
> - "MMAP_CHECK",
> - "BPRM_CHECK",
> - "MODULE_CHECK",
> - "FIRMWARE_CHECK",
> - "POST_SETATTR",
> - "KEXEC_KERNEL_CHECK",
> - "KEXEC_INITRAMFS_CHECK",
> - "POLICY_CHECK"
> + __ima_hooks(__ima_hook_stringify)
> };
>
> void *ima_policy_start(struct seq_file *m, loff_t *pos)
> @@ -949,49 +936,16 @@ void ima_policy_stop(struct seq_file *m, void *v)
>
> #define pt(token) policy_tokens[token + Opt_err].pattern
> #define mt(token) mask_tokens[token]
> -#define ft(token) func_tokens[token]
>
> /*
> * policy_func_show - display the ima_hooks policy rule
> */
> static void policy_func_show(struct seq_file *m, enum ima_hooks func)
> {
> - char tbuf[64] = {0,};
> -
> - switch (func) {
> - case FILE_CHECK:
> - seq_printf(m, pt(Opt_func), ft(func_file));
> - break;
> - case MMAP_CHECK:
> - seq_printf(m, pt(Opt_func), ft(func_mmap));
> - break;
> - case BPRM_CHECK:
> - seq_printf(m, pt(Opt_func), ft(func_bprm));
> - break;
> - case MODULE_CHECK:
> - seq_printf(m, pt(Opt_func), ft(func_module));
> - break;
> - case FIRMWARE_CHECK:
> - seq_printf(m, pt(Opt_func), ft(func_firmware));
> - break;
> - case POST_SETATTR:
> - seq_printf(m, pt(Opt_func), ft(func_post));
> - break;
> - case KEXEC_KERNEL_CHECK:
> - seq_printf(m, pt(Opt_func), ft(func_kexec_kernel));
> - break;
> - case KEXEC_INITRAMFS_CHECK:
> - seq_printf(m, pt(Opt_func), ft(func_kexec_initramfs));
> - break;
> - case POLICY_CHECK:
> - seq_printf(m, pt(Opt_func), ft(func_policy));
> - break;
> - default:
> - snprintf(tbuf, sizeof(tbuf), "%d", func);
> - seq_printf(m, pt(Opt_func), tbuf);
> - break;
> - }
> - seq_puts(m, " ");
> + if (func > 0 && func < MAX_CHECK)
> + seq_printf(m, "func=%s ", func_tokens[func]);
> + else
> + seq_printf(m, "func=%d ", func);

The only time this can happen is when __kernel_read_file_id() is
updated without updating the read_idmap[].  Perhaps we can display the
number and the appropriate __kernel_read_file_id string.

Mimi

> }
>
> int ima_policy_show(struct seq_file *m, void *v)

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