Messages in this thread | | | Date | Tue, 20 Dec 2022 11:36:50 +0100 | Subject | Re: [PATCH] lib/mpi: Fix buffer overrun when SG is too long | From | Roberto Sassu <> |
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On 12/20/2022 8:24 AM, Herbert Xu wrote: > On Mon, Dec 19, 2022 at 09:49:29AM +0100, Roberto Sassu wrote: >> >> do you have any news on this bug? > > Thanks for the reminder. Could you please try this patch?
Tried, could not boot the UML kernel.
After looking, it seems we have to call sg_miter_stop(). Or alternatively, we could let sg_miter_next() be called but not writing anything inside the loop.
With either of those fixes, the tests pass (using one scatterlist).
Roberto
> ---8<--- > The helper mpi_read_raw_from_sgl ignores the second parameter > nbytes when reading the SG list and may overrun its own buffer > because it only allocates enough memory according to nbytes. > > Fixes: 2d4d1eea540b ("lib/mpi: Add mpi sgl helpers") > Reported-by: Roberto Sassu <roberto.sassu@huaweicloud.com> > Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> > > diff --git a/lib/mpi/mpicoder.c b/lib/mpi/mpicoder.c > index 39c4c6731094..6bffc68c1a5a 100644 > --- a/lib/mpi/mpicoder.c > +++ b/lib/mpi/mpicoder.c > @@ -494,17 +494,15 @@ MPI mpi_read_raw_from_sgl(struct scatterlist *sgl, unsigned int nbytes) > val->sign = 0; > val->nlimbs = nlimbs; > > - if (nbytes == 0) > - return val; > - > j = nlimbs - 1; > a = 0; > z = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB; > z %= BYTES_PER_MPI_LIMB; > > - while (sg_miter_next(&miter)) { > + while (nbytes && sg_miter_next(&miter)) { > buff = miter.addr; > - len = miter.length; > + len = min_t(unsigned, miter.length, nbytes); > + nbytes -= len; > > for (x = 0; x < len; x++) { > a <<= 8;
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