Messages in this thread | | | From | Linus Torvalds <> | Date | Tue, 22 Dec 2020 14:01:21 -0800 | Subject | Re: kernel BUG at lib/string.c:LINE! (6) |
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On Tue, Dec 22, 2020 at 6:44 AM syzbot <syzbot+e86f7c428c8c50db65b4@syzkaller.appspotmail.com> wrote: > > The issue was bisected to: > > commit 2f78788b55ba ("ilog2: improve ilog2 for constant arguments")
That looks unlikely, although possibly some constant folding improvement might make the fortify code notice something with it.
> detected buffer overflow in strlen > ------------[ cut here ]------------ > kernel BUG at lib/string.c:1149! > Call Trace: > strlen include/linux/string.h:325 [inline] > strlcpy include/linux/string.h:348 [inline] > xt_rateest_tg_checkentry+0x2a5/0x6b0 net/netfilter/xt_RATEEST.c:143
Honestly, this just looks like the traditional bug in "strlcpy()".
That BSD function is complete garbage, exactly because it doesn't limit the source length. People tend to _think_ it does ("what's that size_t argument for?") but strlcpy() only limits the *destination* size, and the source is always read fully.
So it's a completely useless function if you can't implicitly trust the source string - but that is almost always why people think they should use it!
Nobody should use it. I really would like to remove it, and let everybody know how incredibly broken sh*t that function is.
Can we please have everybody stop using strlcpy(). But in this particular case, it's that xt_rateest_tg_checkentry() in net/netfilter/xt_RATEEST.c
That said, this may be a real FORTIFY report if that info->name is *supposed* to be trustworthy? The xt_RATETEST code does use "info->name" a few lines earlier when it does
est = __xt_rateest_lookup(xn, info->name);
or maybe the bisection is right, and this points to some problem with __builtin_clzll?
Linus
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