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. Thanks for getting it all landed! :) -Kees -- Kees Cook
