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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Daniel Axtens <dja@axtens.net>
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Date: Tue, 8 Mar 2022 23:47:46 +1100
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Subject: [PATCH] net/netbuff: Block overly large netbuff allocs
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A netbuff shouldn't be too huge. It's bounded by MTU and TCP segment
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reassembly.
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This helps avoid some bugs (and provides a spot to instrument to catch
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them at their source).
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Signed-off-by: Daniel Axtens <dja@axtens.net>
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Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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(cherry picked from commit ee9591103004cd13b4efadda671536090ca7fd57)
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---
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grub-core/net/netbuff.c | 13 +++++++++++++
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1 file changed, 13 insertions(+)
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diff --git a/grub-core/net/netbuff.c b/grub-core/net/netbuff.c
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index dbeeefe478..d5e9e9a0d7 100644
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--- a/grub-core/net/netbuff.c
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+++ b/grub-core/net/netbuff.c
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@@ -79,10 +79,23 @@ grub_netbuff_alloc (grub_size_t len)
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COMPILE_TIME_ASSERT (NETBUFF_ALIGN % sizeof (grub_properly_aligned_t) == 0);
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+ /*
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+ * The largest size of a TCP packet is 64 KiB, and everything else
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+ * should be a lot smaller - most MTUs are 1500 or less. Cap data
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+ * size at 64 KiB + a buffer.
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+ */
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+ if (len > 0xffffUL + 0x1000UL)
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+ {
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+ grub_error (GRUB_ERR_BUG,
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+ "attempted to allocate a packet that is too big");
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+ return NULL;
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+ }
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+
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if (len < NETBUFFMINLEN)
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len = NETBUFFMINLEN;
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len = ALIGN_UP (len, NETBUFF_ALIGN);
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+
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#ifdef GRUB_MACHINE_EMU
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data = grub_malloc (len + sizeof (*nb));
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#else
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