linux-stable/lib/mpi
Nicolai Stange ab1e912ec1 lib/mpi: mpi_read_raw_from_sgl(): don't include leading zero SGEs in nbytes
At the very beginning of mpi_read_raw_from_sgl(), the leading zeros of
the input scatterlist are counted:

  lzeros = 0;
  for_each_sg(sgl, sg, ents, i) {
    ...
    if (/* sg contains nonzero bytes */)
      break;

    /* sg contains nothing but zeros here */
    ents--;
    lzeros = 0;
  }

Later on, the total number of trailing nonzero bytes is calculated by
subtracting the number of leading zero bytes from the total number of input
bytes:

  nbytes -= lzeros;

However, since lzeros gets reset to zero for each completely zero leading
sg in the loop above, it doesn't include those.

Besides wasting resources by allocating a too large output buffer,
this mistake propagates into the calculation of x, the number of
leading zeros within the most significant output limb:

  x = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;

What's more, the low order bytes of the output, equal in number to the
extra bytes in nbytes, are left uninitialized.

Fix this by adjusting nbytes for each completely zero leading scatterlist
entry.

Fixes: 2d4d1eea54 ("lib/mpi: Add mpi sgl helpers")
Signed-off-by: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2016-04-05 20:35:50 +08:00
..
generic_mpih-add1.c
generic_mpih-lshift.c
generic_mpih-mul1.c
generic_mpih-mul2.c
generic_mpih-mul3.c
generic_mpih-rshift.c
generic_mpih-sub1.c
longlong.h lib/mpi: avoid assembler warning 2016-02-28 03:26:34 +08:00
Makefile MPILIB: Reinstate mpi_cmp[_ui]() and export for RSA signature verification 2012-10-08 13:50:15 +10:30
mpi-bit.c MPILIB: Provide count_leading/trailing_zeros() based on arch functions 2012-10-08 13:50:11 +10:30
mpi-cmp.c MPILIB: Fix comparison of negative MPIs 2015-01-14 16:10:12 +00:00
mpi-inline.h lib/mpi: use "static inline" instead of "extern inline" 2016-02-28 03:26:34 +08:00
mpi-internal.h lib/mpi: use "static inline" instead of "extern inline" 2016-02-28 03:26:34 +08:00
mpi-pow.c MPILIB: Provide count_leading/trailing_zeros() based on arch functions 2012-10-08 13:50:11 +10:30
mpicoder.c lib/mpi: mpi_read_raw_from_sgl(): don't include leading zero SGEs in nbytes 2016-04-05 20:35:50 +08:00
mpih-cmp.c
mpih-div.c Remove unused code from MPI library 2012-05-26 11:51:03 +10:00
mpih-mul.c Remove unused code from MPI library 2012-05-26 11:51:03 +10:00
mpiutil.c MPILIB: add mpi_read_buf() and mpi_get_size() helpers 2015-06-16 14:35:06 +08:00