[edk2-devel] [PATCH v2 3/4] EmbeddedPkg/Hob: Integer Overflow in CreateHob()

["Guo, Gua" <gua.guo@intel.com>]

From: Gua Guo <gua.guo@intel.com>

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4166

Fix integer overflow in various CreateHob instances.
Fixes: CVE-2022-36765

The CreateHob() function aligns the requested size to 8
performing the following operation:
```
HobLength = (UINT16)((HobLength + 0x7) & (~0x7));
```

No checks are performed to ensure this value doesn't
overflow, and could lead to CreateHob() returning a smaller
HOB than requested, which could lead to OOB HOB accesses.

Reported-by: Marc Beatove <mbeatove@google.com>
Cc: Leif Lindholm <quic_llindhol@quicinc.com>
Reviewed-by: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Abner Chang <abner.chang@amd.com>
Cc: John Mathew <john.mathews@intel.com>
Authored-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Gua Guo <gua.guo@intel.com>
---
 EmbeddedPkg/Library/PrePiHobLib/Hob.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/EmbeddedPkg/Library/PrePiHobLib/Hob.c b/EmbeddedPkg/Library/PrePiHobLib/Hob.c
index 8eb175aa96..1fe3ea93e4 100644
--- a/EmbeddedPkg/Library/PrePiHobLib/Hob.c
+++ b/EmbeddedPkg/Library/PrePiHobLib/Hob.c
@@ -110,6 +110,13 @@ CreateHob (
 
   HandOffHob = GetHobList ();
 
+  //
+  // Check Length to avoid data overflow.
+  //
+  if (HobLength > MAX_UINT16 - 0x7) {
+    return NULL;
+  }
+
   HobLength = (UINT16)((HobLength + 0x7) & (~0x7));
 
   FreeMemory = HandOffHob->EfiFreeMemoryTop - HandOffHob->EfiFreeMemoryBottom;
-- 
2.39.2.windows.1



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