> On Oct 12, 2023, at 4:13 PM, Kees Cook <keescook@xxxxxxxxxxxx> wrote: > > !-------------------------------------------------------------------| > This Message Is From an External Sender > > |-------------------------------------------------------------------! > > On Thu, Oct 12, 2023 at 07:55:55PM +0000, Nick Terrell wrote: >> >>> On Oct 9, 2023, at 1:29 PM, Kees Cook <keescook@xxxxxxxxxxxx> wrote: >>> >>> !-------------------------------------------------------------------| >>> This Message Is From an External Sender >>> >>> |-------------------------------------------------------------------! >>> >>> On Sat, Oct 07, 2023 at 02:05:56PM -0700, Eric Biggers wrote: >>>> Hi Nick, >>>> >>>> On Wed, Aug 30, 2023 at 12:49:53AM -0700, syzbot wrote: >>>>> UBSAN: array-index-out-of-bounds in lib/zstd/common/fse_decompress.c:345:30 >>>>> index 33 is out of range for type 'FSE_DTable[1]' (aka 'unsigned int[1]') >>>> >>>> Zstandard needs to be converted to use C99 flex-arrays instead of length-1 >>>> arrays. https://github.com/facebook/zstd/pull/3785 would fix this in upstream >>>> Zstandard, though it doesn't work well with the fact that upstream Zstandard >>>> supports C90. Not sure how you want to handle this. >>> >>> For the kernel, we just need: >>> >>> diff --git a/lib/zstd/common/fse_decompress.c b/lib/zstd/common/fse_decompress.c >>> index a0d06095be83..b11e87fff261 100644 >>> --- a/lib/zstd/common/fse_decompress.c >>> +++ b/lib/zstd/common/fse_decompress.c >>> @@ -312,7 +312,7 @@ size_t FSE_decompress_wksp(void* dst, size_t dstCapacity, const void* cSrc, size >>> >>> typedef struct { >>> short ncount[FSE_MAX_SYMBOL_VALUE + 1]; >>> - FSE_DTable dtable[1]; /* Dynamically sized */ >>> + FSE_DTable dtable[]; /* Dynamically sized */ >>> } FSE_DecompressWksp; >> >> Thanks Eric and Kees for the report and the fix! I am working on putting this >> patch up now, just need to test the fix myself to ensure I can reproduce the >> issue and the fix. >> >> In your opinion does this worth trying to get this patch into v6.6, or should it >> wait for v6.7? > > For all these flex array conversions we're mostly on a "slow and steady" > route, so there's no rush really. I think waiting for v6.7 is fine. If > anyone ends up wanting to backport it, it should be pretty clean > I imagine. Sounds good, thanks for the context! I’ll make sure the fix gets backported. Eric Biggers already has a PR up! [0] [0] https://github.com/facebook/zstd/pull/3785 > Thanks for getting it all landed! :) > > -Kees > > -- > Kees Cook
