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tomoyo: Limit wildcard recursion depth.

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Since wildcards that need recursion consume kernel stack memory (or might
cause CPU stall warning problem), we cannot allow infinite recursion.

Since TOMOYO 1.8 survived with 20 recursions limit for 5 years, nobody
would complain if applying this limit to TOMOYO 2.6.

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
This commit is contained in:
Tetsuo Handa 2020-11-03 13:17:40 +09:00
parent d9594e0409
commit e991a40b3d
1 changed files with 30 additions and 25 deletions
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55
security/tomoyo/util.c
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@ -434,59 +434,64 @@ void tomoyo_normalize_line(unsigned char *buffer)
*/ */
static bool tomoyo_correct_word2(const char *string, size_t len) static bool tomoyo_correct_word2(const char *string, size_t len)
{ {
u8 recursion = 20;
const char *const start = string; const char *const start = string;
bool in_repetition = false; bool in_repetition = false;
unsigned char c;
unsigned char d;
unsigned char e;
if (!len) if (!len)
goto out; goto out;
while (len--) { while (len--) {
c = *string++; unsigned char c = *string++;
if (c == '\\') { if (c == '\\') {
if (!len--) if (!len--)
goto out; goto out;
c = *string++; c = *string++;
if (c >= '0' && c <= '3') {
unsigned char d;
unsigned char e;
if (!len-- || !len--)
goto out;
d = *string++;
e = *string++;
if (d < '0' || d > '7' || e < '0' || e > '7')
goto out;
c = tomoyo_make_byte(c, d, e);
if (c <= ' ' || c >= 127)
continue;
goto out;
}
switch (c) { switch (c) {
case '\\': /* "\\" */ case '\\': /* "\\" */
continue;
case '$': /* "\$" */
case '+': /* "\+" */ case '+': /* "\+" */
case '?': /* "\?" */ case '?': /* "\?" */
case 'x': /* "\x" */
case 'a': /* "\a" */
case '-': /* "\-" */
continue;
}
if (!recursion--)
goto out;
switch (c) {
case '*': /* "\*" */ case '*': /* "\*" */
case '@': /* "\@" */ case '@': /* "\@" */
case 'x': /* "\x" */ case '$': /* "\$" */
case 'X': /* "\X" */ case 'X': /* "\X" */
case 'a': /* "\a" */
case 'A': /* "\A" */ case 'A': /* "\A" */
case '-': /* "\-" */
continue; continue;
case '{': /* "/\{" */ case '{': /* "/\{" */
if (string - 3 < start || *(string - 3) != '/') if (string - 3 < start || *(string - 3) != '/')
break; goto out;
in_repetition = true; in_repetition = true;
continue; continue;
case '}': /* "\}/" */ case '}': /* "\}/" */
if (*string != '/') if (*string != '/')
break; goto out;
if (!in_repetition) if (!in_repetition)
break; goto out;
in_repetition = false; in_repetition = false;
continue; continue;
case '0': /* "\ooo" */
case '1':
case '2':
case '3':
if (!len-- || !len--)
break;
d = *string++;
e = *string++;
if (d < '0' || d > '7' || e < '0' || e > '7')
break;
c = tomoyo_make_byte(c, d, e);
if (c <= ' ' || c >= 127)
continue;
} }
goto out; goto out;
} else if (in_repetition && c == '/') { } else if (in_repetition && c == '/') {