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From 4ea64c827f8bc57180772fd5671ddd010cb7b2ed Mon Sep 17 00:00:00 2001
From: Daniel Axtens <dja@axtens.net>
Date: Tue, 8 Mar 2022 23:47:46 +1100
Subject: net/netbuff: Block overly large netbuff allocs
A netbuff shouldn't be too huge. It's bounded by MTU and TCP segment
reassembly.
This helps avoid some bugs (and provides a spot to instrument to catch
them at their source).
Signed-off-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
grub-core/net/netbuff.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/grub-core/net/netbuff.c b/grub-core/net/netbuff.c
index dbeeefe47..d5e9e9a0d 100644
--- a/grub-core/net/netbuff.c
+++ b/grub-core/net/netbuff.c
@@ -79,10 +79,23 @@ grub_netbuff_alloc (grub_size_t len)
COMPILE_TIME_ASSERT (NETBUFF_ALIGN % sizeof (grub_properly_aligned_t) == 0);
+ /*
+ * The largest size of a TCP packet is 64 KiB, and everything else
+ * should be a lot smaller - most MTUs are 1500 or less. Cap data
+ * size at 64 KiB + a buffer.
+ */
+ if (len > 0xffffUL + 0x1000UL)
+ {
+ grub_error (GRUB_ERR_BUG,
+ "attempted to allocate a packet that is too big");
+ return NULL;
+ }
+
if (len < NETBUFFMINLEN)
len = NETBUFFMINLEN;
len = ALIGN_UP (len, NETBUFF_ALIGN);
+
#ifdef GRUB_MACHINE_EMU
data = grub_malloc (len + sizeof (*nb));
#else
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