| From 3e4817538de828319ba6d59ced2fbb9b5ca13287 Mon Sep 17 00:00:00 2001 |
| From: Daniel Axtens <dja@axtens.net> |
| Date: Mon, 20 Dec 2021 19:41:21 +1100 |
| Subject: [PATCH] net/ip: Do IP fragment maths safely |
| |
| We can receive packets with invalid IP fragmentation information. This |
| can lead to rsm->total_len underflowing and becoming very large. |
| |
| Then, in grub_netbuff_alloc(), we add to this very large number, which can |
| cause it to overflow and wrap back around to a small positive number. |
| The allocation then succeeds, but the resulting buffer is too small and |
| subsequent operations can write past the end of the buffer. |
| |
| Catch the underflow here. |
| |
| Fixes: CVE-2022-28733 |
| |
| Signed-off-by: Daniel Axtens <dja@axtens.net> |
| Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com> |
| |
| Upstream-Status: Backport |
| CVE: CVE-2022-28733 |
| |
| Reference to upstream patch: |
| https://git.savannah.gnu.org/cgit/grub.git/commit/?id=3e4817538de828319ba6d59ced2fbb9b5ca13287 |
| |
| Signed-off-by: Yongxin Liu <yongxin.liu@windriver.com> |
| |
| --- |
| grub-core/net/ip.c | 10 +++++++++- |
| 1 file changed, 9 insertions(+), 1 deletion(-) |
| |
| diff --git a/grub-core/net/ip.c b/grub-core/net/ip.c |
| index e3d62e97f..3c3d0be0e 100644 |
| --- a/grub-core/net/ip.c |
| +++ b/grub-core/net/ip.c |
| @@ -25,6 +25,7 @@ |
| #include <grub/net/netbuff.h> |
| #include <grub/mm.h> |
| #include <grub/priority_queue.h> |
| +#include <grub/safemath.h> |
| #include <grub/time.h> |
| |
| struct iphdr { |
| @@ -512,7 +513,14 @@ grub_net_recv_ip4_packets (struct grub_net_buff *nb, |
| { |
| rsm->total_len = (8 * (grub_be_to_cpu16 (iph->frags) & OFFSET_MASK) |
| + (nb->tail - nb->data)); |
| - rsm->total_len -= ((iph->verhdrlen & 0xf) * sizeof (grub_uint32_t)); |
| + |
| + if (grub_sub (rsm->total_len, (iph->verhdrlen & 0xf) * sizeof (grub_uint32_t), |
| + &rsm->total_len)) |
| + { |
| + grub_dprintf ("net", "IP reassembly size underflow\n"); |
| + return GRUB_ERR_NONE; |
| + } |
| + |
| rsm->asm_netbuff = grub_netbuff_alloc (rsm->total_len); |
| if (!rsm->asm_netbuff) |
| { |
| -- |
| 2.34.1 |
| |