[bug report] lib/mpi: Extend the MPI library

[Dan Carpenter <dan.carpenter@xxxxxxxxxx>]

Hello Tianjia Zhang,

The patch a8ea8bdd9df9: "lib/mpi: Extend the MPI library" from Sep
21, 2020 (linux-next), leads to the following Smatch static checker
warning:

lib/crypto/mpi/mpiutil.c:202 mpi_copy() error: potential null dereference 'b'.  (mpi_alloc returns null)
lib/crypto/mpi/mpiutil.c:224 mpi_alloc_like() error: potential null dereference 'b'.  (mpi_alloc returns null)
lib/crypto/mpi/mpiutil.c:258 mpi_set() error: potential null dereference 'w'.  (<unknown> returns null)
lib/crypto/mpi/mpiutil.c:277 mpi_set_ui() error: potential null dereference 'w'.  (<unknown> returns null)
lib/crypto/mpi/mpiutil.c:289 mpi_alloc_set_ui() error: potential null dereference 'w'.  (mpi_alloc returns null)

lib/crypto/mpi/mpiutil.c
    195 MPI mpi_copy(MPI a)
    196 {
    197         int i;
    198         MPI b;
    199 
    200         if (a) {
    201                 b = mpi_alloc(a->nlimbs);

Allocations can fail.

--> 202                 b->nlimbs = a->nlimbs;
    203                 b->sign = a->sign;
    204                 b->flags = a->flags;
    205                 b->flags &= ~(16|32); /* Reset the immutable and constant flags. */
    206                 for (i = 0; i < b->nlimbs; i++)
    207                         b->d[i] = a->d[i];
    208         } else
    209                 b = NULL;
    210         return b;
    211 }

regards,
dan carpenter