On 08/18/2016 04:54 PM, [email protected] wrote:
> From: William Roberts <[email protected]>
>
> Rather than duplicating the following sequence:
> 1. Read len from file
> 2. alloc up space based on 1
> 3. read the contents into the buffer from 2
> 4. null terminate the buffer from 2
>
> Use the str_read() function that is in the kernel, which
> collapses steps 2 and 4. This not only reduces redundant
> code, but also has the side-affect of providing a central
> check on zero_or_saturated lengths from step 1 when
> generating string values.
>
> Signed-off-by: William Roberts <[email protected]>
> ---
> libsepol/src/conditional.c | 9 +------
> libsepol/src/module.c | 66
> ++++++++++++++++++++++------------------------
> libsepol/src/policydb.c | 10 +------
> libsepol/src/private.h | 1 +
> libsepol/src/services.c | 33 +++++++++++++++++++++++
> 5 files changed, 68 insertions(+), 51 deletions(-)
>
> diff --git a/libsepol/src/conditional.c b/libsepol/src/conditional.c
> index 8680eb2..e1bc961 100644
> --- a/libsepol/src/conditional.c
> +++ b/libsepol/src/conditional.c
> @@ -589,15 +589,8 @@ int cond_read_bool(policydb_t * p,
> goto err;
>
> len = le32_to_cpu(buf[2]);
> - if (zero_or_saturated(len))
> + if (str_read(&key, fp, len))
> goto err;
> - key = malloc(len + 1);
> - if (!key)
> - goto err;
> - rc = next_entry(key, fp, len);
> - if (rc < 0)
> - goto err;
> - key[len] = 0;
>
> if (p->policy_type != POLICY_KERN &&
> p->policyvers >= MOD_POLICYDB_VERSION_TUNABLE_SEP) {
> diff --git a/libsepol/src/module.c b/libsepol/src/module.c
> index f25df95..a9d7c54 100644
> --- a/libsepol/src/module.c
> +++ b/libsepol/src/module.c
> @@ -793,26 +793,26 @@ int sepol_module_package_info(struct sepol_policy_file
> *spf, int *type,
> i);
> goto cleanup;
> }
> +
> len = le32_to_cpu(buf[0]);
> - if (zero_or_saturated(len)) {
> - ERR(file->handle,
> - "invalid module name length: 0x%"PRIx32,
> - len);
> - goto cleanup;
> - }
> - *name = malloc(len + 1);
> - if (!*name) {
> - ERR(file->handle, "out of memory");
> - goto cleanup;
> - }
> - rc = next_entry(*name, file, len);
> - if (rc < 0) {
> - ERR(file->handle,
> - "cannot get module name string (at section
> %u)",
> - i);
> + if (str_read(name, file, len)) {
> + switch(rc) {
> + case EINVAL:
> + ERR(file->handle,
> + "invalid module name length:
> 0x%"PRIx32,
> + len);
> + break;
> + case ENOMEM:
> + ERR(file->handle, "out of memory");
> + break;
> + default:
> + ERR(file->handle,
> + "cannot get module name string
> (at section %u)",
> + i);
> + }
1) You didn't set rc = str_read(), so you can't switch on it above.
2) Using positive values for errors is likely to confuse matters when
interacting with the existing code, which always uses negative values
(either -errno as a legacy of common code with the kernel or -1).
3) I think this overcomplicates the error handling / reporting. If
str_read() were to set errno and return -1 instead, then you could just
include strerror(errno) in a single error message. Or you can just
always report the most general error message. But it isn't worth a
switch statement.
Same applies throughout.
> goto cleanup;
> }
> - (*name)[len] = '\0';
> +
> rc = next_entry(buf, file, sizeof(uint32_t));
> if (rc < 0) {
> ERR(file->handle,
> @@ -821,25 +821,23 @@ int sepol_module_package_info(struct sepol_policy_file
> *spf, int *type,
> goto cleanup;
> }
> len = le32_to_cpu(buf[0]);
> - if (zero_or_saturated(len)) {
> - ERR(file->handle,
> - "invalid module version length: 0x%"PRIx32,
> - len);
> - goto cleanup;
> - }
> - *version = malloc(len + 1);
> - if (!*version) {
> - ERR(file->handle, "out of memory");
> - goto cleanup;
> - }
> - rc = next_entry(*version, file, len);
> - if (rc < 0) {
> - ERR(file->handle,
> - "cannot get module version string (at
> section %u)",
> - i);
> + if (str_read(version, file, len)) {
> + switch(rc) {
> + case EINVAL:
> + ERR(file->handle,
> + "invalid module name length:
> 0x%"PRIx32,
> + len);
> + break;
> + case ENOMEM:
> + ERR(file->handle, "out of memory");
> + break;
> + default:
> + ERR(file->handle,
> + "cannot get module version
> string (at section %u)",
> + i);
> + }
> goto cleanup;
> }
> - (*version)[len] = '\0';
> seen |= SEEN_MOD;
> break;
> default:
> diff --git a/libsepol/src/policydb.c b/libsepol/src/policydb.c
> index 5f888d3..cdb3cde 100644
> --- a/libsepol/src/policydb.c
> +++ b/libsepol/src/policydb.c
> @@ -1911,19 +1911,11 @@ static int perm_read(policydb_t * p
> goto bad;
>
> len = le32_to_cpu(buf[0]);
> - if (zero_or_saturated(len))
> + if(str_read(&key, fp, len))
> goto bad;
>
> perdatum->s.value = le32_to_cpu(buf[1]);
>
> - key = malloc(len + 1);
> - if (!key)
> - goto bad;
> - rc = next_entry(key, fp, len);
> - if (rc < 0)
> - goto bad;
> - key[len] = 0;
> -
> if (hashtab_insert(h, key, perdatum))
> goto bad;
>
> diff --git a/libsepol/src/private.h b/libsepol/src/private.h
> index 0beb4d4..b884c23 100644
> --- a/libsepol/src/private.h
> +++ b/libsepol/src/private.h
> @@ -65,3 +65,4 @@ extern struct policydb_compat_info
> *policydb_lookup_compat(unsigned int version,
> extern int next_entry(void *buf, struct policy_file *fp, size_t bytes)
> hidden;
> extern size_t put_entry(const void *ptr, size_t size, size_t n,
> struct policy_file *fp) hidden;
> +extern int str_read(char **strp, struct policy_file *fp, size_t len) hidden;
> diff --git a/libsepol/src/services.c b/libsepol/src/services.c
> index d2b80b4..f61f692 100644
> --- a/libsepol/src/services.c
> +++ b/libsepol/src/services.c
> @@ -1679,6 +1679,39 @@ size_t hidden put_entry(const void *ptr, size_t size,
> size_t n,
> }
>
> /*
> + * Reads a string and null terminates it from the policy file.
> + * This is a port of str_read from the SE Linux kernel code.
> + *
> + * It returns:
> + * 0 - Success
> + * EINVAL - len is no good
> + * ENOMEM - allocation failed
> + * or any error possible from next_entry().
> + */
> +int hidden str_read(char **strp, struct policy_file *fp, size_t len)
> +{
> + int rc;
> + char *str;
> +
> + if (zero_or_saturated(len))
> + return EINVAL;
> +
> + str = malloc(len + 1);
> + if (!str)
> + return ENOMEM;
> +
> + /* it's expected the caller should free the str */
> + *strp = str;
> +
> + rc = next_entry(str, fp, len);
> + if (rc)
> + return rc;
> +
> + str[len] = '\0';
> + return 0;
> +}
> +
> +/*
> * Read a new set of configuration data from
> * a policy database binary representation file.
> *
>
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