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libmount: handle arbitrary line length for mounts 

Based on patch from Kees Cook, he wrote:
> The kernel's maximum path length is PATH_MAX (4096). The use of BUFSIZ
> (8192) would seem sufficient for reading mountinfo files, but it's
> not. Paths may contain escaped characters (requiring 4x as many bytes
> to read), and filesystem options are of unknown length. To avoid
> mounts being either intentionally or unintentionally hidden from
> libmount and its users, we must accept arbitrary length lines when
> parsing.
>
> Long valid entries are currently ignored, with warnings like this:
> mount: /proc/self/mountinfo: parse error: ignore entry at line 11.
> mount: /proc/self/mountinfo: parse error: ignore entry at line 12.
>
> Instead of using a malloc on every line parsed from mount files, do it
> once per mount file context, growing it as needed. The general case
> will never grow it.

I have moved the parser stuff to the new struct libmnt_parser, maybe
we can move more things (e.g. libmnt_table->fmt) to this struct later.

Reported-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Karel Zak <kzak@redhat.com>
This commit is contained in:
Karel Zak 2015-08-27 10:49:39 +02:00
parent 0a9e11af22
commit d92b8c3ba1
1 changed files with 49 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

81
libmount/src/tab_parse.c
View File

@ -22,6 +22,22 @@
#include "pathnames.h"
#include "strutils.h"
struct libmnt_parser {
FILE *f; /* fstab, mtab, swaps or mountinfo ... */
char *filename; /* file name or NULL */
char *buf; /* buffer (the current line content) */
size_t bufsiz; /* size of the buffer */
size_t line; /* current line */
};
static void parser_cleanup(struct libmnt_parser *pa)
{
if (!pa)
return;
free(pa->buf);
memset(pa, 0, sizeof(*pa));
}
static int next_number(char **s, int *num)
{
char *end = NULL;
@ -378,16 +394,15 @@ static int is_terminated_by_blank(const char *str)
* 1 if the line is not a comment
* <0 on error
*/
static int next_comment_line(char *buf, size_t bufsz,
FILE *f, char **last, int *nlines)
static int next_comment_line(struct libmnt_parser *pa, char **last)
{
if (fgets(buf, bufsz, f) == NULL)
return feof(f) ? 1 : -EINVAL;
if (getline(&pa->buf, &pa->bufsiz, pa->f) < 0)
return feof(pa->f) ? 1 : -errno;
++*nlines;
*last = strchr(buf, '\n');
pa->line++;
*last = strchr(pa->buf, '\n');
return is_comment_line(buf) ? 0 : 1;
return is_comment_line(pa->buf) ? 0 : 1;
}
static int append_comment(struct libmnt_table *tb,
@ -420,36 +435,35 @@ static int append_comment(struct libmnt_table *tb,
/*
* Read and parse the next line from {fs,m}tab or mountinfo
*/
static int mnt_table_parse_next(struct libmnt_table *tb, FILE *f,
struct libmnt_fs *fs,
const char *filename, int *nlines)
static int mnt_table_parse_next(struct libmnt_parser *pa,
struct libmnt_table *tb,
struct libmnt_fs *fs)
{
char buf[BUFSIZ];
char *s;
int rc;
assert(tb);
assert(f);
assert(pa);
assert(fs);
/* read the next non-blank non-comment line */
next_line:
do {
if (fgets(buf, sizeof(buf), f) == NULL)
if (getline(&pa->buf, &pa->bufsiz, pa->f) < 0)
return -EINVAL;
++*nlines;
s = strchr (buf, '\n');
pa->line++;
s = strchr(pa->buf, '\n');
if (!s) {
/* Missing final newline? Otherwise an extremely */
/* long line - assume file was corrupted */
if (feof(f)) {
if (feof(pa->f)) {
DBG(TAB, ul_debugobj(tb,
"%s: no final newline", filename));
s = strchr (buf, '\0');
"%s: no final newline", pa->filename));
s = strchr(pa->buf, '\0');
} else {
DBG(TAB, ul_debugobj(tb,
"%s:%d: missing newline at line",
filename, *nlines));
"%s:%zu: missing newline at line",
pa->filename, pa->line));
goto err;
}
}
@ -457,16 +471,14 @@ next_line:
/* comments parser */
if (tb->comms
&& (tb->fmt == MNT_FMT_GUESS || tb->fmt == MNT_FMT_FSTAB)
&& is_comment_line(buf)) {
&& is_comment_line(pa->buf)) {
do {
rc = append_comment(tb, fs, buf, feof(f));
rc = append_comment(tb, fs, pa->buf, feof(pa->f));
if (!rc)
rc = next_comment_line(buf,
sizeof(buf),
f, &s, nlines);
rc = next_comment_line(pa, &s);
} while (rc == 0);
if (rc == 1 && feof(f))
if (rc == 1 && feof(pa->f))
rc = append_comment(tb, fs, NULL, 1);
if (rc < 0)
return rc;
@ -474,9 +486,9 @@ next_line:
}
*s = '\0';
if (--s >= buf && *s == '\r')
if (--s >= pa->buf && *s == '\r')
*s = '\0';
s = (char *) skip_blank(buf);
s = (char *) skip_blank(pa->buf);
} while (*s == '\0' || *s == '#');
if (tb->fmt == MNT_FMT_GUESS) {
@ -508,7 +520,7 @@ next_line:
if (rc == 0)
return 0;
err:
DBG(TAB, ul_debugobj(tb, "%s:%d: %s parse error", filename, *nlines,
DBG(TAB, ul_debugobj(tb, "%s:%zu: %s parse error", pa->filename, pa->line,
tb->fmt == MNT_FMT_MOUNTINFO ? "mountinfo" :
tb->fmt == MNT_FMT_SWAPS ? "swaps" :
tb->fmt == MNT_FMT_FSTAB ? "tab" : "utab"));
@ -516,7 +528,7 @@ err:
/* by default all errors are recoverable, otherwise behavior depends on
* the errcb() function. See mnt_table_set_parser_errcb().
*/
return tb->errcb ? tb->errcb(tb, filename, *nlines) : 1;
return tb->errcb ? tb->errcb(tb, pa->filename, pa->line) : 1;
}
static pid_t path_to_tid(const char *filename)
@ -595,11 +607,11 @@ static int kernel_fs_postparse(struct libmnt_table *tb,
*/
int mnt_table_parse_stream(struct libmnt_table *tb, FILE *f, const char *filename)
{
int nlines = 0;
int rc = -1;
int flags = 0;
pid_t tid = -1;
struct libmnt_fs *fs = NULL;
struct libmnt_parser pa = { .line = 0 };
assert(tb);
assert(f);
@ -609,6 +621,9 @@ int mnt_table_parse_stream(struct libmnt_table *tb, FILE *f, const char *filenam
filename, mnt_table_get_nents(tb),
tb->fltrcb ? "yes" : "not"));
pa.filename = filename;
pa.f = f;
/* necessary for /proc/mounts only, the /proc/self/mountinfo
* parser sets the flag properly
*/
@ -622,7 +637,7 @@ int mnt_table_parse_stream(struct libmnt_table *tb, FILE *f, const char *filenam
goto err;
}
rc = mnt_table_parse_next(tb, f, fs, filename, &nlines);
rc = mnt_table_parse_next(&pa, tb, fs);
if (!rc && tb->fltrcb && tb->fltrcb(fs, tb->fltrcb_data))
rc = 1; /* filtered out by callback... */
@ -653,9 +668,11 @@ int mnt_table_parse_stream(struct libmnt_table *tb, FILE *f, const char *filenam
DBG(TAB, ul_debugobj(tb, "%s: stop parsing (%d entries)",
filename, mnt_table_get_nents(tb)));
parser_cleanup(&pa);
return 0;
err:
DBG(TAB, ul_debugobj(tb, "%s: parse error (rc=%d)", filename, rc));
parser_cleanup(&pa);
return rc;
}