| Message ID | 1458648768-1469-11-git-send-email-nicstange@gmail.com (mailing list archive) |
|---|---|
| State | Accepted |
| Delegated to: | Herbert Xu |
| Headers | show |
diff --git a/lib/mpi/mpicoder.c b/lib/mpi/mpicoder.c index 048f0aa..4ba0f23 100644 --- a/lib/mpi/mpicoder.c +++ b/lib/mpi/mpicoder.c @@ -447,16 +447,12 @@ MPI mpi_read_raw_from_sgl(struct scatterlist *sgl, unsigned int nbytes) break; ents--; + nbytes -= lzeros; lzeros = 0; } sgl = sg; - - if (!ents) - nbytes = 0; - else - nbytes -= lzeros; - + nbytes -= lzeros; nbits = nbytes * 8; if (nbits > MAX_EXTERN_MPI_BITS) { pr_info("MPI: mpi too large (%u bits)\n", nbits);
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: 2d4d1eea540b ("lib/mpi: Add mpi sgl helpers") Signed-off-by: Nicolai Stange <nicstange@gmail.com> --- lib/mpi/mpicoder.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-)