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authorNicolai Stange <nicstange@gmail.com>2016-03-22 15:17:27 +0300
committerHerbert Xu <herbert@gondor.apana.org.au>2016-04-05 15:35:51 +0300
commit64c09b0b59b92ad231dd526f57f24139b728044b (patch)
tree848eb86e6d3968c0896ba6fd865b89c3441eb4ec /lib/mpi
parent60e1b74c224e9eda14e5b479413c5d990373c2cb (diff)
downloadlinux-64c09b0b59b92ad231dd526f57f24139b728044b.tar.xz
lib/mpi: mpi_read_raw_from_sgl(): fix nbits calculation
The number of bits, nbits, is calculated in mpi_read_raw_from_sgl() as follows: nbits = nbytes * 8; Afterwards, the number of leading zero bits of the first byte get subtracted: nbits -= count_leading_zeros(*(u8 *)(sg_virt(sgl) + lzeros)); However, count_leading_zeros() takes an unsigned long and thus, the u8 gets promoted to an unsigned long. Thus, the above doesn't subtract the number of leading zeros in the most significant nonzero input byte from nbits, but the number of leading zeros of the most significant nonzero input byte promoted to unsigned long, i.e. BITS_PER_LONG - 8 too many. Fix this by subtracting count_leading_zeros(...) - (BITS_PER_LONG - 8) from nbits only. Fixes: 2d4d1eea540b ("lib/mpi: Add mpi sgl helpers") Signed-off-by: Nicolai Stange <nicstange@gmail.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'lib/mpi')
-rw-r--r--lib/mpi/mpicoder.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/lib/mpi/mpicoder.c b/lib/mpi/mpicoder.c
index 27703aad287a..24a015513b40 100644
--- a/lib/mpi/mpicoder.c
+++ b/lib/mpi/mpicoder.c
@@ -460,7 +460,8 @@ MPI mpi_read_raw_from_sgl(struct scatterlist *sgl, unsigned int nbytes)
}
if (nbytes > 0)
- nbits -= count_leading_zeros(*(u8 *)(sg_virt(sgl) + lzeros));
+ nbits -= count_leading_zeros(*(u8 *)(sg_virt(sgl) + lzeros)) -
+ (BITS_PER_LONG - 8);
nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
val = mpi_alloc(nlimbs);