diff options
author | Jesper Juhl <jj@chaosbits.net> | 2012-02-06 04:07:04 -0500 |
---|---|---|
committer | James Morris <james.l.morris@oracle.com> | 2012-04-17 22:14:28 -0400 |
commit | 09c79b60960bdd4b00916219402eabfa5e479c5a (patch) | |
tree | d8be1892ca81cbd194ac5e8c198f0f939d432257 /lib | |
parent | 86812bb0de1a3758dc6c7aa01a763158a7c0638a (diff) |
mpi: Avoid using freed pointer in mpi_lshift_limbs()
At the start of the function we assign 'a->d' to 'ap'. Then we use the
RESIZE_IF_NEEDED macro on 'a' - this may free 'a->d' and replace it
with newly allocaetd storage. In that case, we'll be operating on
freed memory further down in the function when we index into 'ap[]'.
Since we don't actually need 'ap' until after the use of the
RESIZE_IF_NEEDED macro we can just delay the assignment to it until
after we've potentially resized, thus avoiding the issue.
While I was there anyway I also changed the integer variable 'n' to be
const. It might as well be since we only assign to it once and use it
as a constant, and then the compiler will tell us if we ever assign to
it in the future.
Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Acked-by: Dmitry Kasatkin <dmitry.kasatkin@intel.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
Diffstat (limited to 'lib')
-rw-r--r-- | lib/mpi/mpi-bit.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/lib/mpi/mpi-bit.c b/lib/mpi/mpi-bit.c index 2f526627e4f5..0c505361da19 100644 --- a/lib/mpi/mpi-bit.c +++ b/lib/mpi/mpi-bit.c | |||
@@ -177,8 +177,8 @@ int mpi_rshift(MPI x, MPI a, unsigned n) | |||
177 | */ | 177 | */ |
178 | int mpi_lshift_limbs(MPI a, unsigned int count) | 178 | int mpi_lshift_limbs(MPI a, unsigned int count) |
179 | { | 179 | { |
180 | mpi_ptr_t ap = a->d; | 180 | const int n = a->nlimbs; |
181 | int n = a->nlimbs; | 181 | mpi_ptr_t ap; |
182 | int i; | 182 | int i; |
183 | 183 | ||
184 | if (!count || !n) | 184 | if (!count || !n) |
@@ -187,6 +187,7 @@ int mpi_lshift_limbs(MPI a, unsigned int count) | |||
187 | if (RESIZE_IF_NEEDED(a, n + count) < 0) | 187 | if (RESIZE_IF_NEEDED(a, n + count) < 0) |
188 | return -ENOMEM; | 188 | return -ENOMEM; |
189 | 189 | ||
190 | ap = a->d; | ||
190 | for (i = n - 1; i >= 0; i--) | 191 | for (i = n - 1; i >= 0; i--) |
191 | ap[i + count] = ap[i]; | 192 | ap[i + count] = ap[i]; |
192 | for (i = 0; i < count; i++) | 193 | for (i = 0; i < count; i++) |