Re: [edk2-devel] [PATCH v3 0/5] OvmfPkg: Use QemuKernelLoaderFs to read cmdline/initrd

["Laszlo Ersek" <lersek@redhat.com>]

On 06/28/21 12:51, Dov Murik wrote:
> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
> 
> In order to support measured SEV boot with kernel/initrd/cmdline, we'd
> like to have one place that reads those blobs; in the future we'll add
> the measurement and verification in that place.
> 
> We already have a synthetic filesystem (QemuKernelLoaderFs) which holds
> three files: "kernel", "initrd", and "cmdline".  The kernel is indeed
> read from this filesystem in LoadImage; but the cmdline (and the length
> of initrd) are read from QemuFwCfgLib items.
> 
> This patch series first fixes two identical memory leak bugs in
> GenericQemuLoadImageLib and X86QemuLoadImageLib; then modifies
> GenericQemuLoadImageLib to read cmdline (and the initrd size) from the
> QemuKernelLoaderFs synthetic filesystem, thus removing the dependency on
> QemuFwCfgLib.
> 
> Note that X86QemuLoadImageLib is not modified, because it contains a
> QemuLoadLegacyImage() which reads other items of the QemuFwCfg which are
> not available in QemuKernelLoaderFs.  Since we don't want to support the
> legacy boot path in the future measured SEV boot, we leave
> X86QemuLoadImageLib as-is (except for a comment addition in patch 3) and
> will force use for GenericQemuLoadImageLib in the measured SEV boot
> implementation.
> 
> Relevant discussion threads start in:
> https://edk2.groups.io/g/devel/message/76069
> 
> To test this on x86_64, I forced the use of GenericQemuLoadImageLib
> using the following local patch:
> 
> 
> diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc
> index 0a237a905866..46442b543bcf 100644
> --- a/OvmfPkg/OvmfPkgX64.dsc
> +++ b/OvmfPkg/OvmfPkgX64.dsc
> @@ -404,7 +404,7 @@ [LibraryClasses.common.DXE_DRIVER]
>    PciLib|OvmfPkg/Library/DxePciLibI440FxQ35/DxePciLibI440FxQ35.inf
>    MpInitLib|UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf
>    QemuFwCfgS3Lib|OvmfPkg/Library/QemuFwCfgS3Lib/DxeQemuFwCfgS3LibFwCfg.inf
> -  QemuLoadImageLib|OvmfPkg/Library/X86QemuLoadImageLib/X86QemuLoadImageLib.inf
> +  QemuLoadImageLib|OvmfPkg/Library/GenericQemuLoadImageLib/GenericQemuLoadImageLib.inf # XXX don't commit this or someone will be mad
>  !if $(TPM_ENABLE) == TRUE
>    Tpm12DeviceLib|SecurityPkg/Library/Tpm12DeviceLibTcg/Tpm12DeviceLibTcg.inf
>    Tpm2DeviceLib|SecurityPkg/Library/Tpm2DeviceLibTcg2/Tpm2DeviceLibTcg2.inf
> 
> 
> I tested boot with QEMU and OVMF with the following QEMU arguments:
> 
>   -kernel a
>   -kernel a -initrd b
>   -kernel a -cmdline c
>   -kernel a -initrd b -cmdline c
> 
> (and also without -kernel)
> 
> 
> Code is at
> https://github.com/confidential-containers-demo/edk2/tree/use-synthetic-fs-for-cmdline-v3
> 
> v3 changes:
>  - Insert patches 1+2 at the top of the series to fix cmdline leak bugs
>  - Organize #include and .inf
>  - Add UINTN overflow check
>  - Fix error paths and function epilogue to properly release all resources
>  - Clarity: rename long variables, reword comments
> 
> v2: https://edk2.groups.io/g/devel/message/76664
> v2 changes:
>  - Add comment to header of X86QemuLoadImageLib.inf
>  - Clearer function names in GenericQemuLoadImageLib.c
>  - Fix coding style issues
> 
> v1: https://edk2.groups.io/g/devel/message/76265
> 
> 
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: James Bottomley <jejb@linux.ibm.com>
> Cc: Tobin Feldman-Fitzthum <tobin@linux.ibm.com>
> 
> 
> Dov Murik (5):
>   OvmfPkg/GenericQemuLoadImageLib: plug cmdline blob leak on success
>   OvmfPkg/X86QemuLoadImageLib: plug cmdline blob leak on success
>   Revert "OvmfPkg/QemuKernelLoaderFsDxe: don't expose kernel command
>     line"
>   OvmfPkg/GenericQemuLoadImageLib: Read cmdline from QemuKernelLoaderFs
>   OvmfPkg/X86QemuLoadImageLib: State fw_cfg dependency in file header
> 
>  OvmfPkg/Library/GenericQemuLoadImageLib/GenericQemuLoadImageLib.inf |   3 +-
>  OvmfPkg/Library/X86QemuLoadImageLib/X86QemuLoadImageLib.inf         |   3 +
>  OvmfPkg/Library/GenericQemuLoadImageLib/GenericQemuLoadImageLib.c   | 157 ++++++++++++++++++--
>  OvmfPkg/Library/X86QemuLoadImageLib/X86QemuLoadImageLib.c           |   9 +-
>  OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.c               |  11 +-
>  5 files changed, 161 insertions(+), 22 deletions(-)
> 

Merged as commit range d1fc3d7ef3cb..9421f5ab8d1e, via
<https://github.com/tianocore/edk2/pull/1770>.

(The BZ remains open for the upcoming (related) patch sets.)

Thanks
Laszlo