Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | From | Yueyi Li <> | Subject | Re: [PATCH v2] lzo: fix ip overrun during compress. | Date | Wed, 5 Dec 2018 03:07:58 +0000 |
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Hi Markus,
Thanks for your review.
On 2018/12/4 18:20, Markus F.X.J. Oberhumer wrote: > Hi, > > I don't think that address space wraparound is legal in C, but I > understand that we are in kernel land and if you really want to > compress the last virtual page 0xfffffffffffff000 the following > small patch should fix that dubious case.
I guess the VA 0xfffffffffffff000 is available because KASLR be enabled. For this case we can see:
crash> kmem 0xfffffffffffff000 PAGE PHYSICAL MAPPING INDEX CNT FLAGS ffffffbfffffffc0 1fffff000 ffffffff1655ecb9 7181fd5 2 8000000000064209 locked,uptodate,owner_priv_1,writeback,reclaim,swapbacked
> This also avoids slowing down the the hot path of the compression > core function. > > Cheers, > Markus > > > > diff --git a/lib/lzo/lzo1x_compress.c b/lib/lzo/lzo1x_compress.c > index 236eb21167b5..959dec45f6fe 100644 > --- a/lib/lzo/lzo1x_compress.c > +++ b/lib/lzo/lzo1x_compress.c > @@ -224,8 +224,8 @@ int lzo1x_1_compress(const unsigned char *in, size_t in_len, > > while (l > 20) { > size_t ll = l <= (M4_MAX_OFFSET + 1) ? l : (M4_MAX_OFFSET + 1); > - uintptr_t ll_end = (uintptr_t) ip + ll; > - if ((ll_end + ((t + ll) >> 5)) <= ll_end) > + // check for address space wraparound > + if (((uintptr_t) ip + ll + ((t + ll) >> 5)) <= (uintptr_t) ip) > break; > BUILD_BUG_ON(D_SIZE * sizeof(lzo_dict_t) > LZO1X_1_MEM_COMPRESS); > memset(wrkmem, 0, D_SIZE * sizeof(lzo_dict_t)); I parsed panic ramdump and loaded CPU register values, can see:
-000|lzo1x_1_do_compress( | in = 0xFFFFFFFFFFFFF000, | ?, | out = 0xFFFFFFFF2E2EE000, | out_len = 0xFFFFFF801CAA3510, | ?, | wrkmem = 0xFFFFFFFF4EBC0000) | dict = 0xFFFFFFFF4EBC0000 | op = 0x1 | ip = 0x9 | ii = 0x9 | in_end = 0x0 | ip_end = 0xFFFFFFFFFFFFFFEC | m_len = 0 | m_off = 1922 -001|lzo1x_1_compress( | in = 0xFFFFFFFFFFFFF000, | in_len = 0, | out = 0xFFFFFFFF2E2EE000, | out_len = 0x00000001616FB7D0, | wrkmem = 0xFFFFFFFF4EBC0000) | ip = 0xFFFFFFFFFFFFF000 | op = 0xFFFFFFFF2E2EE000 | l = 4096 | t = 0 | ll = 4096 ll = l = in_len = 4096 in lzo1x_1_compress, so your patch is working for this panic case, but, I`m not sure, is it possible that in = 0xFFFFFFFFFFFFF000 and in_len < 4096?
Thanks, Yueyi
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