| Message ID | Y6FjQPZiJYTEG1zI@gondor.apana.org.au (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | lib/mpi: Fix buffer overrun when SG is too long | expand |
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;
On Tue, Dec 20, 2022 at 11:36:50AM +0100, Roberto Sassu wrote: > 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; I think it should look like: while (nbytes) { sg_miter_next(&miter); ... } sg_miter_stop(&miter); - Eric
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;