Messages in this thread Patch in this message | | | From | Rusty Russell <> | Subject | Re: [PATCH] kernel: kallsyms: memory override issue, need check destination buffer length | Date | Thu, 11 Apr 2013 13:38:15 +0930 |
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Chen Gang <gang.chen@asianux.com> writes: > We don't export any symbols > 128 characters, but if we did then > kallsyms_expand_symbol() would overflow the buffer handed to it. > So we need check destination buffer length when copying. > > the related test: > if we define an EXPORT function which name more than 128. > will panic when call kallsyms_lookup_name by init_kprobes on booting. > after check the length (provide this patch), it is ok. > > Implementaion: > add additional destination buffer length parameter (maxlen) > if uncompressed string is too long (>= maxlen), it will be truncated. > not check the parameters whether valid, since it is a static function. > > > Signed-off-by: Chen Gang <gang.chen@asianux.com> > Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
??!!! I never signed this off! I've never seen it before!
Minor comments below:
> -static unsigned int kallsyms_expand_symbol(unsigned int off, char *result) > +static unsigned int kallsyms_expand_symbol(unsigned int off, > + char *result, int maxlen)
'size_t maxlen' would be more explicit.
> { > int len, skipped_first = 0; > const u8 *tptr, *data; > + char *begin = result; > /* Get the compressed symbol length from the first symbol byte. */ > data = &kallsyms_names[off]; > @@ -113,14 +116,16 @@ static unsigned int kallsyms_expand_symbol(unsigned int off, char *result) > while (*tptr) { > if (skipped_first) { > - *result = *tptr; > - result++; > + *result++ = *tptr; > + if (result - begin == maxlen - 1) > + goto tail;
You could just decrement maxlen instead, and handle maxlen == 0 at the same time:
if (maxlen <= 1) goto tail; *result = *tptr; result++; maxlen--;
> @@ -176,7 +181,7 @@ unsigned long kallsyms_lookup_name(const char *name) > unsigned int off; > for (i = 0, off = 0; i < kallsyms_num_syms; i++) { > - off = kallsyms_expand_symbol(off, namebuf); > + off = kallsyms_expand_symbol(off, namebuf, sizeof(namebuf)); > if (strcmp(namebuf, name) == 0) > return kallsyms_addresses[i];
I prefer to use ARRAY_SIZE(namebuf) instead of sizeof(namebuf). That way we break compile if the declaration is changed from an array to a pointer one day.
Same for the others.
Thanks, Rusty.
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