[Xen-devel] [PATCH 04/11] OvmfPkg/XenBusDxe: Avoid Allocate in XenStoreVSPrint

From: Anthony PERARD <anthony.perard@citrix.com>
To: <devel@edk2.groups.io>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Jordan Justen <jordan.l.justen@intel.com>,
	Julien Grall <julien.grall@arm.com>,
	Anthony Perard <anthony.perard@citrix.com>,
	xen-devel@lists.xenproject.org, Laszlo Ersek <lersek@redhat.com>
Subject: [Xen-devel] [PATCH 04/11] OvmfPkg/XenBusDxe: Avoid Allocate in XenStoreVSPrint
Date: Fri, 13 Sep 2019 15:50:53 +0100	[thread overview]
Message-ID: <20190913145100.303433-5-anthony.perard@citrix.com> (raw)
In-Reply-To: <20190913145100.303433-1-anthony.perard@citrix.com>

In order to be able to use XenStoreVSPrint during the
ExitBootServices, we remove the allocation done by the function and
use the stack instead.

Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2190
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
---
 OvmfPkg/XenBusDxe/XenStore.c | 21 +++++++++------------
 1 file changed, 9 insertions(+), 12 deletions(-)

diff --git a/OvmfPkg/XenBusDxe/XenStore.c b/OvmfPkg/XenBusDxe/XenStore.c
index 5cc900190a..7b71dc156d 100644
--- a/OvmfPkg/XenBusDxe/XenStore.c
+++ b/OvmfPkg/XenBusDxe/XenStore.c
@@ -1259,20 +1259,17 @@ XenStoreVSPrint (
   IN VA_LIST               Marker
   )
 {
-  CHAR8 *Buf;
-  XENSTORE_STATUS Status;
-  UINTN BufSize;
-  VA_LIST Marker2;
+  CHAR8           Buf[XENSTORE_PAYLOAD_MAX];
+  UINTN           Count;
 
-  VA_COPY (Marker2, Marker);
-  BufSize = SPrintLengthAsciiFormat (FormatString, Marker2) + 1;
-  VA_END (Marker2);
-  Buf = AllocateZeroPool (BufSize);
-  AsciiVSPrint (Buf, BufSize, FormatString, Marker);
-  Status = XenStoreWrite (Transaction, DirectoryPath, Node, Buf);
-  FreePool (Buf);
+  Count = AsciiVSPrint (Buf, sizeof (Buf), FormatString, Marker);
+  ASSERT (Count > 0);
+  ASSERT (Count < sizeof (Buf));
+  if ((Count == 0) || (Count >= sizeof (Buf))) {
+    return XENSTORE_STATUS_EINVAL;
+  }
 
-  return Status;
+  return XenStoreWrite (Transaction, DirectoryPath, Node, Buf);
 }
 
 XENSTORE_STATUS
-- 
Anthony PERARD

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