Messages in this thread | | | Date | Thu, 12 Apr 2012 09:20:33 +0300 | Subject | Re: [PATCH] mpi: Avoid using freed pointer in mpi_lshift_limbs() | From | "Kasatkin, Dmitry" <> |
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On Thu, Apr 12, 2012 at 1:31 AM, Jesper Juhl <jj@chaosbits.net> wrote: > On Tue, 13 Mar 2012, Kasatkin, Dmitry wrote: > >> On Thu, Mar 1, 2012 at 11:33 PM, Jesper Juhl <jj@chaosbits.net> wrote: >> > >> > Ping? >> > >> > On Mon, 6 Feb 2012, Jesper Juhl wrote: >> > >> >> 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> >> >> --- >> >> lib/mpi/mpi-bit.c | 5 +++-- >> >> 1 files changed, 3 insertions(+), 2 deletions(-) >> >> >> >> only compile tested. >> >> >> >> diff --git a/lib/mpi/mpi-bit.c b/lib/mpi/mpi-bit.c >> >> index 2f52662..0c50536 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) >> >> */ >> >> int mpi_lshift_limbs(MPI a, unsigned int count) >> >> { >> >> - mpi_ptr_t ap = a->d; >> >> - int n = a->nlimbs; >> >> + const int n = a->nlimbs; >> >> + mpi_ptr_t ap; >> >> int i; >> >> >> >> if (!count || !n) >> >> @@ -187,6 +187,7 @@ int mpi_lshift_limbs(MPI a, unsigned int count) >> >> if (RESIZE_IF_NEEDED(a, n + count) < 0) >> >> return -ENOMEM; >> >> >> >> + ap = a->d; >> >> for (i = n - 1; i >= 0; i--) >> >> ap[i + count] = ap[i]; >> >> for (i = 0; i < count; i++) >> >> >> > >> > -- >> > Jesper Juhl <jj@chaosbits.net> http://www.chaosbits.net/ >> > Don't top-post http://www.catb.org/jargon/html/T/top-post.html >> > Plain text mails only, please. >> > >> > -- >> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >> > the body of a message to majordomo@vger.kernel.org >> > More majordomo info at http://vger.kernel.org/majordomo-info.html >> > Please read the FAQ at http://www.tux.org/lkml/ >> >> Hello, >> >> I was travelling last week. >> I will review the patch now.. >> > > Hi. > > Did you get a chance to review the patch? Did you find it acceptable or > flawed? > > If it is OK, what do I need to from this point forward to get it merged? > >
Hello Jesper & James,
That is of course correct.
James, can you please apply this patch to security fixes?
Acked-by: Dmitry Kasatkin <dmitry.kasatkin@intel.com>
- Dmitry
> -- > Jesper Juhl <jj@chaosbits.net> http://www.chaosbits.net/ > Don't top-post http://www.catb.org/jargon/html/T/top-post.html > Plain text mails only, please. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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