> -----Original Message-----
> From: Stephen Smalley [mailto:s...@tycho.nsa.gov]
> Sent: Thursday, September 8, 2016 8:15 AM
> To: Roberts, William C <william.c.robe...@intel.com>; selinux@tycho.nsa.gov;
> seandroid-l...@tycho.nsa.gov; jwca...@tycho.nsa.gov
> Subject: Re: [PATCH v2] libselinux: clean up process file
>
> On 09/06/2016 08:07 PM, william.c.robe...@intel.com wrote:
> > From: William Roberts <william.c.robe...@intel.com>
> >
> > The current process_file() code will open the file twice on the case
> > of a binary file, correct this.
> >
> > The general flow through process_file() was a bit difficult to read,
> > streamline the routine to be more readable.
> >
> > Detailed statistics of before and after:
> >
> > Source lines of code reported by cloc on modified files:
> > before: 735
> > after: 740
> >
> > Object size difference:
> > before: 195530 bytes
> > after: 195529 bytes
> >
> > Signed-off-by: William Roberts <william.c.robe...@intel.com>
> > ---
> > libselinux/src/label_file.c | 263
> > ++++++++++++++++++++++++--------------------
> > 1 file changed, 145 insertions(+), 118 deletions(-)
> >
> > diff --git a/libselinux/src/label_file.c b/libselinux/src/label_file.c
> > index c89bb35..6839a77 100644
> > --- a/libselinux/src/label_file.c
> > +++ b/libselinux/src/label_file.c
> > @@ -97,62 +97,43 @@ static int nodups_specs(struct saved_data *data, const
> char *path)
> > return rc;
> > }
> >
> > -static int load_mmap(struct selabel_handle *rec, const char *path,
> > - struct stat *sb, bool isbinary,
> > - struct selabel_digest *digest)
> > +static int process_text_file(FILE *fp, const char *prefix, struct
> > +selabel_handle *rec, const char *path) {
> > + /*
> > + * Then do detailed validation of the input and fill the spec array
> > + */
>
> You can drop this comment; it is no longer helpful/relevant.
>
> > + int rc;
> > + size_t line_len;
> > + unsigned lineno = 0;
> > + char *line_buf = NULL;
> > +
> > + while (getline(&line_buf, &line_len, fp) > 0) {
> > + rc = process_line(rec, path, prefix, line_buf, ++lineno);
> > + if (rc)
> > + goto out;
> > + }
> > + rc = 0;
> > +out:
> > + free(line_buf);
> > + return rc;
> > +}
> > +
> > +static int load_mmap(FILE *fp, size_t len, struct selabel_handle
> > +*rec, const char *path)
> > {
> > struct saved_data *data = (struct saved_data *)rec->data;
> > - char mmap_path[PATH_MAX + 1];
> > - int mmapfd;
> > int rc;
> > - struct stat mmap_stat;
> > char *addr, *str_buf;
> > - size_t len;
> > int *stem_map;
> > struct mmap_area *mmap_area;
> > uint32_t i, magic, version;
> > uint32_t entry_len, stem_map_len, regex_array_len;
> >
> > - if (isbinary) {
> > - len = strlen(path);
> > - if (len >= sizeof(mmap_path))
> > - return -1;
> > - strcpy(mmap_path, path);
> > - } else {
> > - rc = snprintf(mmap_path, sizeof(mmap_path), "%s.bin", path);
> > - if (rc >= (int)sizeof(mmap_path))
> > - return -1;
> > - }
> > -
> > - mmapfd = open(mmap_path, O_RDONLY | O_CLOEXEC);
> > - if (mmapfd < 0)
> > - return -1;
> > -
> > - rc = fstat(mmapfd, &mmap_stat);
> > - if (rc < 0) {
> > - close(mmapfd);
> > - return -1;
> > - }
> > -
> > - /* if mmap is old, ignore it */
> > - if (mmap_stat.st_mtime < sb->st_mtime) {
> > - close(mmapfd);
> > - return -1;
> > - }
> > -
> > - /* ok, read it in... */
> > - len = mmap_stat.st_size;
> > - len += (sysconf(_SC_PAGE_SIZE) - 1);
> > - len &= ~(sysconf(_SC_PAGE_SIZE) - 1);
> > -
> > mmap_area = malloc(sizeof(*mmap_area));
> > if (!mmap_area) {
> > - close(mmapfd);
> > return -1;
> > }
I just noticed this, I made this a single line if and didn't drop the braces,
this
Will be in v3
> >
> > - addr = mmap(NULL, len, PROT_READ, MAP_PRIVATE, mmapfd, 0);
> > - close(mmapfd);
> > + addr = mmap(NULL, len, PROT_READ, MAP_PRIVATE, fileno(fp), 0);
> > if (addr == MAP_FAILED) {
> > free(mmap_area);
> > perror("mmap");
> > @@ -306,7 +287,7 @@ static int load_mmap(struct selabel_handle *rec, const
> char *path,
> > if (strcmp(spec->lr.ctx_raw, "<<none>>") && rec->validating) {
> > if (selabel_validate(rec, &spec->lr) < 0) {
> > selinux_log(SELINUX_ERROR,
> > - "%s: context %s is invalid\n",
> mmap_path, spec->lr.ctx_raw);
> > + "%s: context %s is invalid\n", path,
> spec->lr.ctx_raw);
> > goto err;
> > }
> > }
> > @@ -408,105 +389,151 @@ static int load_mmap(struct selabel_handle *rec,
> const char *path,
> > data->nspec++;
> > }
> >
> > - rc = digest_add_specfile(digest, NULL, addr, mmap_stat.st_size,
> > - mmap_path);
> > - if (rc)
> > - goto err;
> > -
>
> We should explicitly set rc = 0 here.
>
> > err:
>
> And maybe this should be out: since it is the only exit path and not only for
> errors.
>
> > free(stem_map);
> >
> > return rc;
> > }
> >
> > -static int process_file(const char *path, const char *suffix,
> > - struct selabel_handle *rec,
> > - const char *prefix, struct selabel_digest *digest)
> > -{
> > - FILE *fp;
> > +struct file_details {
> > + const char *suffix;
> > struct stat sb;
> > - unsigned int lineno;
> > - size_t line_len = 0;
> > - char *line_buf = NULL;
> > - int rc;
> > - char stack_path[PATH_MAX + 1];
> > - bool isbinary = false;
> > +};
> > +
> > +static char *rolling_append(char *current, const char *suffix, size_t
> > +max) {
> > + size_t size;
> > + size_t suffix_size;
> > + size_t current_size;
> > +
> > + if (!suffix)
> > + return current;
> > +
> > + /*
> > + * Overflow check that the following
> > + * arithmatec will not overflow or
> > + */
>
> I think you can drop the comment, or if not, fix the spelling and drop the
> trailing
> or.
>
> > + current_size = strlen(current);
> > + suffix_size = strlen(suffix);
> > +
> > + size = current_size + suffix_size;
> > + if (size < current_size || size < suffix_size)
> > + return NULL;
> > +
> > + /* ensure space for the '.' and the '\0' characters. */
> > + if (size >= (SIZE_MAX - 2))
> > + return NULL;
> > +
> > + size += 2;
> > +
> > + if (size > max)
> > + return NULL;
> > +
> > + /* Append any given suffix */
> > + char *to = stpcpy(¤t[current_size], ".");
>
> Simpler as:
> char *to = current + current_size;
> *to++ = '.';
>
> > + strcat(to, suffix);
> > +
> > + return current;
> > +}
> > +
> > +static bool fcontext_is_binary(FILE *fp) {
> > uint32_t magic;
> >
> > - /* append the path suffix if we have one */
> > - if (suffix) {
> > - rc = snprintf(stack_path, sizeof(stack_path),
> > - "%s.%s", path, suffix);
> > - if (rc >= (int)sizeof(stack_path)) {
> > - errno = ENAMETOOLONG;
> > - return -1;
> > - }
> > - path = stack_path;
> > + size_t len = fread(&magic, sizeof(magic), 1, fp);
> > + rewind(fp);
> > +
> > + return (len && (magic == SELINUX_MAGIC_COMPILED_FCONTEXT));
> > +}
> > +
> > +#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
> > +
> > +static FILE *open_file(const char *path, const char *suffix,
> > + char *save_path, size_t len, struct stat *sb) {
> > + unsigned i;
> > + int rc;
> > + char stack_path[len];
>
> Ew, what is this? C99 magic. Probably just make it PATH_MAX and be done with
> it.
>
> > + struct file_details *found = NULL;
> > +
> > + /*
> > + * Rolling append of suffix. Try to open with path.suffix then the
> > + * next as path.suffix.suffix and so forth.
> > + */
> > + struct file_details fdetails[2] = {
> > + { .suffix = suffix },
> > + { .suffix = "bin" }
> > + };
> > +
> > + rc = snprintf(stack_path, sizeof(stack_path), "%s", path);
>
> What does gcc yield as sizeof(stack_path) here since it is dynamically sized?
>
> > + if (rc >= (int) sizeof(stack_path)) {
> > + errno = ENAMETOOLONG;
> > + return NULL;
> > }
> >
> > - /* Open the specification file. */
> > - fp = fopen(path, "r");
> > - if (fp) {
> > - __fsetlocking(fp, FSETLOCKING_BYCALLER);
> > + for (i = 0; i < ARRAY_SIZE(fdetails); i++) {
> >
> > - if (fstat(fileno(fp), &sb) < 0)
> > - return -1;
> > - if (!S_ISREG(sb.st_mode)) {
> > - errno = EINVAL;
> > - return -1;
> > - }
> > + /* This handles the case if suffix is null */
> > + path = rolling_append(stack_path, fdetails[i].suffix,
> > + sizeof(stack_path));
> > + if (!path)
> > + return NULL;
> >
> > - magic = 0;
> > - if (fread(&magic, sizeof magic, 1, fp) != 1) {
> > - if (ferror(fp)) {
> > - errno = EINVAL;
> > - fclose(fp);
> > - return -1;
> > - }
> > - clearerr(fp);
> > - }
> > + rc = stat(path, &fdetails[i].sb);
> > + if (rc)
> > + continue;
> >
> > - if (magic == SELINUX_MAGIC_COMPILED_FCONTEXT) {
> > - /* file_contexts.bin format */
> > - fclose(fp);
> > - fp = NULL;
> > - isbinary = true;
> > - } else {
> > - rewind(fp);
> > + /* first file thing found, just take it */
> > + if (!found) {
> > + strcpy(save_path, path);
> > + found = &fdetails[i];
> > + continue;
> > }
> > - } else {
> > +
> > /*
> > - * Text file does not exist, so clear the timestamp
> > - * so that we will always pass the timestamp comparison
> > - * with the bin file in load_mmap().
> > + * Keep picking the newest file found. Where "newest"
> > + * includes equality. This provides a precedence on
> > + * secondary suffixes even when the timestamp is the
> > + * same. Ie choose file_contexts.bin over file_contexts
> > + * even if the time stamp is the same.
> > */
> > - sb.st_mtime = 0;
> > + if (fdetails[i].sb.st_mtime >= found->sb.st_mtime) {
> > + found = &fdetails[i];
> > + strcpy(save_path, path);
> > + }
> > }
> >
> > - rc = load_mmap(rec, path, &sb, isbinary, digest);
> > - if (rc == 0)
> > - goto out;
> > + if (!found) {
> > + errno = ENOENT;
> > + return NULL;
> > + }
> >
> > - if (!fp)
> > - return -1; /* no text or bin file */
> > + memcpy(sb, &found->sb, sizeof(*sb));
> > + return fopen(save_path, "r");
> > +}
> >
> > - /*
> > - * Then do detailed validation of the input and fill the spec array
> > - */
> > - lineno = 0;
> > - rc = 0;
> > - while (getline(&line_buf, &line_len, fp) > 0) {
> > - rc = process_line(rec, path, prefix, line_buf, ++lineno);
> > - if (rc)
> > - goto out;
> > - }
> > +static int process_file(const char *path, const char *suffix,
> > + struct selabel_handle *rec,
> > + const char *prefix, struct selabel_digest *digest) {
> > + int rc;
> > + struct stat sb;
> > + FILE *fp = NULL;
> > + char found_path[PATH_MAX + 1];
>
> I think this is wrong elsewhere too but technically these only need to be
> PATH_MAX since that includes the NUL terminator and also avoids unnecessarily
> crossing another page boundary.
>
> > +
> > + fp = open_file(path, suffix, found_path, sizeof(found_path), &sb);
> > + if (fp == NULL)
> > + return -1;
> >
> > - rc = digest_add_specfile(digest, fp, NULL, sb.st_size, path);
> > + rc = fcontext_is_binary(fp) ?
> > + load_mmap(fp, sb.st_size, rec, found_path) :
> > + process_text_file(fp, prefix, rec, found_path);
> > + if (rc < 0)
> > + goto out;
> >
> > + rc = digest_add_specfile(digest, fp, NULL, sb.st_size, found_path);
> > out:
> > - free(line_buf);
> > - if (fp)
> > - fclose(fp);
> > + fclose(fp);
> > return rc;
> > }
> >
> >
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