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Commit bd3fc8133b2b ("ShellPkg/App: Fix memory leak and save resources.",
2016-05-20) added a FreePool() call for Split->SplitStdIn, near end of the
RunSplitCommand(), right after the same shell file was closed with
CloseFile(). The argument was:
> 1) RunSplitCommand() allocates the initial SplitStdOut via
> CreateFileInterfaceMem(). Free SplitStdIn after the swap to fix
> the memory leak.
There is no memory leak actually, and the FreePool() call in question
constitutes a double-free:
(a) This is how the handle is established:
ConvertEfiFileProtocolToShellHandle (
CreateFileInterfaceMem (Unicode),
NULL
);
CreateFileInterfaceMem() allocates an EFI_FILE_PROTOCOL_MEM object and
populates it fully. ConvertEfiFileProtocolToShellHandle() allocates
some administrative structures and links the EFI_FILE_PROTOCOL_MEM
object into "mFileHandleList".
(b) EFI_SHELL_PROTOCOL.CloseFile() is required to close the
SHELL_FILE_HANDLE and to release all associated data. Accordingly,
near the end of RunSplitCommand(), we have:
EfiShellClose()
ShellFileHandleRemove()
//
// undoes the effects of ConvertEfiFileProtocolToShellHandle()
//
ConvertShellHandleToEfiFileProtocol()
//
// note that this does not adjust the pointer value; it's a pure
// type cast
//
FileHandleClose()
FileInterfaceMemClose()
//
// tears down EFI_FILE_PROTOCOL_MEM completely, undoing the
// effects of CreateFileInterfaceMem ()
//
The FreePool() call added by bd3fc8133b2b conflicts with
SHELL_FREE_NON_NULL(This);
in FileInterfaceMemClose(), so remove it.
This error can be reproduced for example with:
> Shell> map | more
> 'more' is not recognized as an internal or external command, operable
> program, or script file.
which triggers:
> ASSERT MdeModulePkg/Core/Dxe/Mem/Pool.c(624): CR has Bad Signature
with the following stack dump:
> #0 0x000000007f6dc094 in CpuDeadLoop () at
> MdePkg/Library/BaseLib/CpuDeadLoop.c:37
> #1 0x000000007f6dd1b4 in DebugAssert (FileName=0x7f6ed9f0
> "MdeModulePkg/Core/Dxe/Mem/Pool.c", LineNumber=624,
> Description=0x7f6ed9d8 "CR has Bad Signature") at
> OvmfPkg/Library/PlatformDebugLibIoPort/DebugLib.c:153
> #2 0x000000007f6d075d in CoreFreePoolI (Buffer=0x7e232c98,
> PoolType=0x7f6bc1c4) at MdeModulePkg/Core/Dxe/Mem/Pool.c:624
> #3 0x000000007f6d060e in CoreInternalFreePool (Buffer=0x7e232c98,
> PoolType=0x7f6bc1c4) at MdeModulePkg/Core/Dxe/Mem/Pool.c:529
> #4 0x000000007f6d0648 in CoreFreePool (Buffer=0x7e232c98) at
> MdeModulePkg/Core/Dxe/Mem/Pool.c:552
> #5 0x000000007d49fbf8 in FreePool (Buffer=0x7e232c98) at
> MdePkg/Library/UefiMemoryAllocationLib/MemoryAllocationLib.c:818
> #6 0x000000007d4875c3 in RunSplitCommand (CmdLine=0x7d898398,
> StdIn=0x0, StdOut=0x0) at ShellPkg/Application/Shell/Shell.c:1813
> #7 0x000000007d487d59 in ProcessNewSplitCommandLine
> (CmdLine=0x7d898398) at ShellPkg/Application/Shell/Shell.c:2121
> #8 0x000000007d488937 in RunShellCommand (CmdLine=0x7e233018,
> CommandStatus=0x0) at ShellPkg/Application/Shell/Shell.c:2670
> #9 0x000000007d488b0b in RunCommand (CmdLine=0x7e233018) at
> ShellPkg/Application/Shell/Shell.c:2732
> #10 0x000000007d4867c8 in DoShellPrompt () at
> ShellPkg/Application/Shell/Shell.c:1349
> #11 0x000000007d48524d in UefiMain (ImageHandle=0x7e24c898,
> SystemTable=0x7f5b6018) at ShellPkg/Application/Shell/Shell.c:631
Cc: Jaben Carsey <jaben.carsey@intel.com>
Cc: Marvin Häuser <Marvin.Haeuser@outlook.com>
Cc: Qiu Shumin <shumin.qiu@intel.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Fixes: bd3fc8133b2b17ad2e0427d1bf6b44b08cf2f3b2
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>
Reviewed-by: Marvin Häuser <Marvin.Haeuser@outlook.com>
============================================================================
OVERVIEW
============================================================================
The UEFI 2.0 shell provides a standard pre-boot command line processor.
It is similar to the EDK EFI Shell or a *nix command line parser.
============================================================================
HOW TO INCORPORATE THIS SHELL INTO NT32
============================================================================
The instructions below are included as a sample and template on how a
developer may integrate this code into an existing platform:
1. Add this shell build to the NT32 build:
Add the shell.inf to the [components] section as it is in the ShellPkg.dsc.
2. Update system PCDs to support this new module
Update the PCD as follows using the Shell's PCD:
gEfiIntelFrameworkModulePkgTokenSpaceGuid.PcdShellFile|{ 0x83, 0xA5, 0x04, 0x7C, 0x3E, 0x9E, 0x1C, 0x4F, 0xAD, 0x65, 0xE0, 0x52, 0x68, 0xD0, 0xB4, 0xD1 }
3. Remove the old shell from the NT32 Firmware list
Remove the FILE APPLICATION section for the old shell.
4. Add this shell to the NT32 firmware list
Add the Shell.INF to the end of the list of DXE modules.
5. Build NT32
============================================================================