2023-07-24 00:34:15

by Mark O'Donovan

Subject: [PATCH] lib/mpi: avoid null pointer deref in mpi_cmp_ui()

During NVMeTCP Authentication a controller can trigger a kernel
oops by specifying the 8192 bit Diffie Hellman group and passing
a correctly sized, but zeroed Diffie Hellamn value.
mpi_cmp_ui() was detecting this if the second parameter was 0,
but 1 is passed from dh_is_pubkey_valid(). This causes the null
pointer u->d to be dereferenced towards the end of mpi_cmp_ui()

Signed-off-by: Mark O'Donovan <[email protected]>
---
lib/mpi/mpi-cmp.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/lib/mpi/mpi-cmp.c b/lib/mpi/mpi-cmp.c
index c4cfa3ff0581..0835b6213235 100644
--- a/lib/mpi/mpi-cmp.c
+++ b/lib/mpi/mpi-cmp.c
@@ -25,8 +25,12 @@ int mpi_cmp_ui(MPI u, unsigned long v)
mpi_limb_t limb = v;

mpi_normalize(u);
- if (!u->nlimbs && !limb)
- return 0;
+ if (u->nlimbs == 0) {
+ if (v == 0)
+ return 0;
+ else
+ return -1;
+ }
if (u->sign)
return -1;
if (u->nlimbs > 1)
--
2.39.2

2023-08-04 09:40:33

by Herbert Xu

Subject: Re: [PATCH] lib/mpi: avoid null pointer deref in mpi_cmp_ui()

On Mon, Jul 24, 2023 at 12:07:27AM +0000, Mark O'Donovan wrote:
> During NVMeTCP Authentication a controller can trigger a kernel
> oops by specifying the 8192 bit Diffie Hellman group and passing
> a correctly sized, but zeroed Diffie Hellamn value.
> mpi_cmp_ui() was detecting this if the second parameter was 0,
> but 1 is passed from dh_is_pubkey_valid(). This causes the null
> pointer u->d to be dereferenced towards the end of mpi_cmp_ui()
>
> Signed-off-by: Mark O'Donovan <[email protected]>
> ---
> lib/mpi/mpi-cmp.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)

Could you please resend this to linux-crypto?

Thanks,
--
Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt