lib/mpi: kunmap after finishing accessing buffer

Using sg_miter_start and sg_miter_next, the buffer of an SG is kmap'ed
to *buff. The current code calls sg_miter_stop (and thus kunmap) on the
SG entry before the last access of *buff.

The patch moves the sg_miter_stop call after the last access to *buff to
ensure that the memory pointed to by *buff is still mapped.

Fixes: 4816c9406430 ("lib/mpi: Fix SG miter leak")
Cc: <stable@vger.kernel.org>
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 3 insertions, 1 deletions

diff --git a/lib/mpi/mpicoder.c b/lib/mpi/mpicoder.c
index 5a0f75a3bf01..eead4b339466 100644
--- a/lib/mpi/mpicoder.c
+++ b/lib/mpi/mpicoder.c
@@ -364,11 +364,11 @@ MPI mpi_read_raw_from_sgl(struct scatterlist *sgl, unsigned int nbytes)
         }
 
         miter.consumed = lzeros;
-        sg_miter_stop(&miter);
 
         nbytes -= lzeros;
         nbits = nbytes * 8;
         if (nbits > MAX_EXTERN_MPI_BITS) {
+                sg_miter_stop(&miter);
                 pr_info("MPI: mpi too large (%u bits)\n", nbits);
                 return NULL;
         }
@@ -376,6 +376,8 @@ MPI mpi_read_raw_from_sgl(struct scatterlist *sgl, unsigned int nbytes)
         if (nbytes > 0)
                 nbits -= count_leading_zeros(*buff) - (BITS_PER_LONG - 8);
 
+        sg_miter_stop(&miter);
+
         nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
         val = mpi_alloc(nlimbs);
         if (!val)