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OvmfPkg/AcpiPlatformDxe: suppress invalid "deref of undef pointer" warning

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RH covscan emits the following false positive:

> Error: CLANG_WARNING:
> edk2-89910a39dcfd/OvmfPkg/AcpiPlatformDxe/AcpiPlatform.c:182:14:
> warning: Dereference of undefined pointer value
> #    Status = FwVol->ReadSection (
> #             ^~~~~~~~~~~~~~~~~~
> edk2-89910a39dcfd/OvmfPkg/AcpiPlatformDxe/AcpiPlatform.c:164:7: note:
> Assuming the condition is false
> #  if (QemuDetected ()) {
> #      ^~~~~~~~~~~~~~~
> edk2-89910a39dcfd/OvmfPkg/AcpiPlatformDxe/AcpiPlatform.c:164:3: note:
> Taking false branch
> #  if (QemuDetected ()) {
> #  ^
> edk2-89910a39dcfd/OvmfPkg/AcpiPlatformDxe/AcpiPlatform.c:174:3: note:
> Taking false branch
> #  if (EFI_ERROR (Status)) {
> #  ^
> edk2-89910a39dcfd/OvmfPkg/AcpiPlatformDxe/AcpiPlatform.c:180:10: note:
> Assuming 'Status' is equal to EFI_SUCCESS
> #  while (Status == EFI_SUCCESS) {
> #         ^~~~~~~~~~~~~~~~~~~~~
> edk2-89910a39dcfd/OvmfPkg/AcpiPlatformDxe/AcpiPlatform.c:180:3: note:
> Loop condition is true.  Entering loop body
> #  while (Status == EFI_SUCCESS) {
> #  ^
> edk2-89910a39dcfd/OvmfPkg/AcpiPlatformDxe/AcpiPlatform.c:182:14: note:
> Dereference of undefined pointer value
> #    Status = FwVol->ReadSection (
> #             ^~~~~~~~~~~~~~~~~~
> #  180|     while (Status == EFI_SUCCESS) {
> #  181|
> #  182|->     Status = FwVol->ReadSection (
> #  183|                         FwVol,
> #  184|                         (EFI_GUID*)PcdGetPtr (PcdAcpiTableStorageFile),

This is invalid because LocateFvInstanceWithTables() sets FwVol on
success.

Suppress the message by:
- assigning FwVol NULL first (this would replace the original report with
  "nullptr deref"),
- asserting that FwVol is no longer NULL, on success.

What's important here is that ASSERT() ends with ANALYZER_UNREACHABLE() on
failure.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Bugzilla: https://bugzilla.tianocore.org/show_bug.cgi?id=1710
Issue: scan-0991.txt
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Philippe Mathieu-Daude <philmd@redhat.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
This commit is contained in:
Laszlo Ersek 2019-04-12 16:45:58 +02:00
parent 52d229238b
commit dc5bbf1074
1 changed files with 7 additions and 0 deletions
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7
OvmfPkg/AcpiPlatformDxe/AcpiPlatform.c
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@ -161,6 +161,11 @@ InstallOvmfFvTables (
TableInstallFunction = InstallAcpiTable; TableInstallFunction = InstallAcpiTable;
} }
//
// set FwVol (and use an ASSERT() below) to suppress incorrect
// compiler/analyzer warnings
//
FwVol = NULL;
// //
// Locate the firmware volume protocol // Locate the firmware volume protocol
// //
@ -168,6 +173,8 @@ InstallOvmfFvTables (
if (EFI_ERROR (Status)) { if (EFI_ERROR (Status)) {
return EFI_ABORTED; return EFI_ABORTED;
} }
ASSERT (FwVol != NULL);
// //
// Read tables from the storage file. // Read tables from the storage file.
// //