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Date: Mon, 12 Aug 2013 12:01:54 -0700
From: Casey Schaufler <casey@...aufler-ca.com>
To: Rafal Krypa <r.krypa@...sung.com>
CC: linux-security-module@...r.kernel.org,
linux-kernel@...r.kernel.org,
Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH] Smack: parse multiple rules per write to load2, up to
PAGE_SIZE-1 bytes
On 8/9/2013 2:47 AM, Rafal Krypa wrote:
> Smack interface for loading rules has always parsed only single rule from
> data written to it. This requires user program to call one write() per
> each rule it wants to load.
> This change makes it possible to write multiple rules, separated by new
> line character. Smack will load at most PAGE_SIZE-1 characters and properly
> return number of processed bytes. In case when user buffer is larger, it
> will be additionally truncated. All characters after last \n will not get
> parsed to avoid partial rule near input buffer boundary.
>
> Signed-off-by: Rafal Krypa <r.krypa@...sung.com>
Acked-by: Casey Schaufler <casey@...aufler-ca.com>
Applied to git://git.gitorious.org/smack-next/kernel.git smack-for-3.12
> ---
> security/smack/smackfs.c | 167 +++++++++++++++++++++++-----------------------
> 1 file changed, 82 insertions(+), 85 deletions(-)
>
> diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
> index a07e93f..80f4b4a 100644
> --- a/security/smack/smackfs.c
> +++ b/security/smack/smackfs.c
> @@ -368,56 +368,43 @@ static int smk_parse_rule(const char *data, struct smack_parsed_rule *rule,
> * @data: string to be parsed, null terminated
> * @rule: Will be filled with Smack parsed rule
> * @import: if non-zero, import labels
> - * @change: if non-zero, data is from /smack/change-rule
> + * @tokens: numer of substrings expected in data
> *
> - * Returns 0 on success, -1 on failure
> + * Returns number of processed bytes on success, -1 on failure.
> */
> -static int smk_parse_long_rule(const char *data, struct smack_parsed_rule *rule,
> - int import, int change)
> +static ssize_t smk_parse_long_rule(char *data, struct smack_parsed_rule *rule,
> + int import, int tokens)
> {
> - char *subject;
> - char *object;
> - char *access1;
> - char *access2;
> - int datalen;
> - int rc = -1;
> + ssize_t cnt = 0;
> + char *tok[4];
> + int i;
>
> - /* This is inefficient */
> - datalen = strlen(data);
> + /*
> + * Parsing the rule in-place, filling all white-spaces with '\0'
> + */
> + for (i = 0; i < tokens; ++i) {
> + while (isspace(data[cnt]))
> + data[cnt++] = '\0';
>
> - /* Our first element can be 64 + \0 with no spaces */
> - subject = kzalloc(datalen + 1, GFP_KERNEL);
> - if (subject == NULL)
> - return -1;
> - object = kzalloc(datalen, GFP_KERNEL);
> - if (object == NULL)
> - goto free_out_s;
> - access1 = kzalloc(datalen, GFP_KERNEL);
> - if (access1 == NULL)
> - goto free_out_o;
> - access2 = kzalloc(datalen, GFP_KERNEL);
> - if (access2 == NULL)
> - goto free_out_a;
> -
> - if (change) {
> - if (sscanf(data, "%s %s %s %s",
> - subject, object, access1, access2) == 4)
> - rc = smk_fill_rule(subject, object, access1, access2,
> - rule, import, 0);
> - } else {
> - if (sscanf(data, "%s %s %s", subject, object, access1) == 3)
> - rc = smk_fill_rule(subject, object, access1, NULL,
> - rule, import, 0);
> + if (data[cnt] == '\0')
> + /* Unexpected end of data */
> + return -1;
> +
> + tok[i] = data + cnt;
> +
> + while (data[cnt] && !isspace(data[cnt]))
> + ++cnt;
> }
> + while (isspace(data[cnt]))
> + data[cnt++] = '\0';
>
> - kfree(access2);
> -free_out_a:
> - kfree(access1);
> -free_out_o:
> - kfree(object);
> -free_out_s:
> - kfree(subject);
> - return rc;
> + while (i < 4)
> + tok[i++] = NULL;
> +
> + if (smk_fill_rule(tok[0], tok[1], tok[2], tok[3], rule, import, 0))
> + return -1;
> +
> + return cnt;
> }
>
> #define SMK_FIXED24_FMT 0 /* Fixed 24byte label format */
> @@ -449,9 +436,10 @@ static ssize_t smk_write_rules_list(struct file *file, const char __user *buf,
> {
> struct smack_parsed_rule rule;
> char *data;
> - int datalen;
> - int rc = -EINVAL;
> - int load = 0;
> + int rc;
> + int trunc = 0;
> + int tokens;
> + ssize_t cnt = 0;
>
> /*
> * No partial writes.
> @@ -466,11 +454,14 @@ static ssize_t smk_write_rules_list(struct file *file, const char __user *buf,
> */
> if (count != SMK_OLOADLEN && count != SMK_LOADLEN)
> return -EINVAL;
> - datalen = SMK_LOADLEN;
> - } else
> - datalen = count + 1;
> + } else {
> + if (count >= PAGE_SIZE) {
> + count = PAGE_SIZE - 1;
> + trunc = 1;
> + }
> + }
>
> - data = kzalloc(datalen, GFP_KERNEL);
> + data = kmalloc(count + 1, GFP_KERNEL);
> if (data == NULL)
> return -ENOMEM;
>
> @@ -479,36 +470,49 @@ static ssize_t smk_write_rules_list(struct file *file, const char __user *buf,
> goto out;
> }
>
> - if (format == SMK_LONG_FMT) {
> - /*
> - * Be sure the data string is terminated.
> - */
> - data[count] = '\0';
> - if (smk_parse_long_rule(data, &rule, 1, 0))
> - goto out;
> - } else if (format == SMK_CHANGE_FMT) {
> - data[count] = '\0';
> - if (smk_parse_long_rule(data, &rule, 1, 1))
> - goto out;
> - } else {
> - /*
> - * More on the minor hack for backward compatibility
> - */
> - if (count == (SMK_OLOADLEN))
> - data[SMK_OLOADLEN] = '-';
> - if (smk_parse_rule(data, &rule, 1))
> + /*
> + * In case of parsing only part of user buf,
> + * avoid having partial rule at the data buffer
> + */
> + if (trunc) {
> + while (count > 0 && (data[count - 1] != '\n'))
> + --count;
> + if (count == 0) {
> + rc = -EINVAL;
> goto out;
> + }
> }
>
> - if (rule_list == NULL) {
> - load = 1;
> - rule_list = &rule.smk_subject->smk_rules;
> - rule_lock = &rule.smk_subject->smk_rules_lock;
> + data[count] = '\0';
> + tokens = (format == SMK_CHANGE_FMT ? 4 : 3);
> + while (cnt < count) {
> + if (format == SMK_FIXED24_FMT) {
> + rc = smk_parse_rule(data, &rule, 1);
> + if (rc != 0) {
> + rc = -EINVAL;
> + goto out;
> + }
> + cnt = count;
> + } else {
> + rc = smk_parse_long_rule(data + cnt, &rule, 1, tokens);
> + if (rc <= 0) {
> + rc = -EINVAL;
> + goto out;
> + }
> + cnt += rc;
> + }
> +
> + if (rule_list == NULL)
> + rc = smk_set_access(&rule, &rule.smk_subject->smk_rules,
> + &rule.smk_subject->smk_rules_lock, 1);
> + else
> + rc = smk_set_access(&rule, rule_list, rule_lock, 0);
> +
> + if (rc)
> + goto out;
> }
>
> - rc = smk_set_access(&rule, rule_list, rule_lock, load);
> - if (rc == 0)
> - rc = count;
> + rc = cnt;
> out:
> kfree(data);
> return rc;
> @@ -1829,7 +1833,6 @@ static ssize_t smk_user_access(struct file *file, const char __user *buf,
> {
> struct smack_parsed_rule rule;
> char *data;
> - char *cod;
> int res;
>
> data = simple_transaction_get(file, buf, count);
> @@ -1842,18 +1845,12 @@ static ssize_t smk_user_access(struct file *file, const char __user *buf,
> res = smk_parse_rule(data, &rule, 0);
> } else {
> /*
> - * Copy the data to make sure the string is terminated.
> + * simple_transaction_get() returns null-terminated data
> */
> - cod = kzalloc(count + 1, GFP_KERNEL);
> - if (cod == NULL)
> - return -ENOMEM;
> - memcpy(cod, data, count);
> - cod[count] = '\0';
> - res = smk_parse_long_rule(cod, &rule, 0, 0);
> - kfree(cod);
> + res = smk_parse_long_rule(data, &rule, 0, 3);
> }
>
> - if (res)
> + if (res < 0)
> return -EINVAL;
>
> res = smk_access(rule.smk_subject, rule.smk_object,
--
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