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ShellPkg: Fix Optional Data rewriting with bcfg 

When modifying the Optional Data of a boot option with bcfg boot -opt
the result was corrupted data, for instance a concatenation of old data,
heap contents, and new data. This was due to a erronous calculation of
the original optional data length.

In addition to fixing the calculation, add explaining comments and
introduce a helper variable, to not abuse other variables and confuse
readers (including the author).

Signed-off-by: Tormod Volden <debian.tormod@gmail.com>
This commit is contained in:
Tormod Volden 2024-07-25 14:30:56 +02:00 committed by mergify[bot]
parent b21cf3bd5b
commit 54469a6918
1 changed files with 9 additions and 5 deletions
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10
ShellPkg/Library/UefiShellBcfgCommandLib/UefiShellBcfgCommandLib.c
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@ -99,6 +99,7 @@ UpdateOptionalData (
UINT8 *OriginalData;
UINTN NewSize;
UINT8 *NewData;
UINTN TmpSize;
UINTN OriginalOptionDataSize;
UnicodeSPrint (VariableName, sizeof (VariableName), L"%s%04x", Target == BcfgTargetBootOrder ? L"Boot" : L"Driver", Index);
@ -135,9 +136,12 @@ UpdateOptionalData (
// Allocate new struct and discard old optional data.
//
ASSERT (OriginalData != NULL);
OriginalOptionDataSize = sizeof (UINT32) + sizeof (UINT16) + StrSize (((CHAR16 *)(OriginalData + sizeof (UINT32) + sizeof (UINT16))));
OriginalOptionDataSize += (*(UINT16 *)(OriginalData + sizeof (UINT32)));
OriginalOptionDataSize -= OriginalSize;
// Length of Attributes, FilePathListLength, Description fields
TmpSize = sizeof (UINT32) + sizeof (UINT16) + StrSize (((CHAR16 *)(OriginalData + sizeof (UINT32) + sizeof (UINT16))));
// Length of FilePathList field
TmpSize += (*(UINT16 *)(OriginalData + sizeof (UINT32)));
// What remains is the original OptionalData field
OriginalOptionDataSize = OriginalSize - TmpSize;
NewSize = OriginalSize - OriginalOptionDataSize + DataSize;
NewData = AllocatePool (NewSize);
if (NewData == NULL) {