On 10/19/23 15:50, Pedro Falcato wrote: > On Wed, Oct 18, 2023 at 6:24 PM Laszlo Ersek <ler...@redhat.com> wrote: >> >> Referring to a file relative to a regular file makes no sense (or at least >> it cannot be implemented consistently with how a file is referred to >> relative to a directory). VirtioFsSimpleFileOpen() has enforced this >> strictly since the beginning, and a few months ago I reported USWG Mantis >> ticket #2367 [1] too, for clearing up the related confusion in the UEFI >> spec. >> >> Unfortunately, the shim boot loader contains such a bug [2] [3]. I don't >> believe the shim bug is ever going to be fixed. We can however relax the >> check in VirtioFsSimpleFileOpen() a bit: if the pathname that's being >> opened relative to a regular file is absolute, then the base file is going >> to be ignored anyway, so we can let the caller's bug slide. This happens >> to make shim work. >> >> Why this matters: UEFI-bootable Linux installer ISOs tend to come with >> shim and grub in the embedded (ElTorito) FAT image (ESP). Sometimes you >> want to build upstream shim/grub binaries, but boot the same ISO >> otherwise. The fastest way for overriding the ESP for this purpose is to >> copy its original contents to a virtio filesystem, then overwrite the shim >> and grub binaries from the host side. Note that this is different from >> direct-booting a kernel (via fw_cfg); the point is to check whether the >> just-built shim and grub are able to boot the rest of the ISO. >> >> [1] https://mantis.uefi.org/mantis/view.php?id=2367 >> [2] https://bugzilla.redhat.com/show_bug.cgi?id=1966973 >> [3] https://github.com/rhboot/shim/issues/382 >> >> Cc: Ard Biesheuvel <ardb+tianoc...@kernel.org> >> Cc: Gerd Hoffmann <kra...@redhat.com> >> Cc: Jiewen Yao <jiewen....@intel.com> >> Cc: Jordan Justen <jordan.l.jus...@intel.com> >> Signed-off-by: Laszlo Ersek <ler...@redhat.com> >> --- >> >> Notes: >> context:-U4 >> >> OvmfPkg/VirtioFsDxe/SimpleFsOpen.c | 17 ++++++++++++++--- >> 1 file changed, 14 insertions(+), 3 deletions(-) >> >> diff --git a/OvmfPkg/VirtioFsDxe/SimpleFsOpen.c >> b/OvmfPkg/VirtioFsDxe/SimpleFsOpen.c >> index a13d4f6a1e2d..2ecf3d6c2325 100644 >> --- a/OvmfPkg/VirtioFsDxe/SimpleFsOpen.c >> +++ b/OvmfPkg/VirtioFsDxe/SimpleFsOpen.c >> @@ -394,22 +394,33 @@ VirtioFsSimpleFileOpen ( >> >> // >> // Referring to a file relative to a regular file makes no sense (or at >> least >> // it cannot be implemented consistently with how a file is referred to >> - // relative to a directory). >> + // relative to a directory). See USWG Mantis ticket #2367. >> // >> if (!VirtioFsFile->IsDirectory) { >> + BOOLEAN BugCompat; >> + >> + // >> + // Tolerate this bug in the caller if FileName is absolute. If FileName >> is >> + // absolute, then VirtioFsAppendPath() below will disregard >> + // VirtioFsFile->CanonicalPathname. >> + // >> + BugCompat = (FileName[0] == L'\\'); >> + >> DEBUG (( >> - DEBUG_ERROR, >> + BugCompat ? DEBUG_WARN : DEBUG_ERROR, >> ("%a: Label=\"%s\" CanonicalPathname=\"%a\" FileName=\"%s\": " >> "nonsensical request to open a file or directory relative to a >> regular " >> "file\n"), >> __func__, >> VirtioFs->Label, >> VirtioFsFile->CanonicalPathname, >> FileName >> )); >> - return EFI_INVALID_PARAMETER; >> + if (!BugCompat) { >> + return EFI_INVALID_PARAMETER; >> + } >> } >> >> // >> // Allocate the new VIRTIO_FS_FILE object. >> > > Aww, you should've CC'd me.
Ouch! I'm sorry. I've grown to (quite mechanically) consult $EDK_TOOLS_PATH/Scripts/GetMaintainer.py for the Cc list :( > Anyway, retroactive > Acked-by: Pedro Falcato <pedro.falc...@gmail.com> Thank you! (I've pushed the patch already, so can't record your A-b on it, but the mailing list will preserve it at least.) > > If this is the new pseudo-sanctioned behavior for filesystem drivers, > I'll make sure to do the same adjustments for Ext4Dxe. > I think that would be useful. (Of course I don't "insist" that you share my opinion on whether this new behavior is for bug compatibility with the UEFI spec and shim (which I think it is), or because it is the right/intuitive thing to do (which I don't think it is) -- just feel entirely free to word the Ext4Pkg comments and commit message as you see fit! ... And I probably don't even have to state this, but let me just state it anyway. :) ) Cheers Laszlo -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#109808): https://edk2.groups.io/g/devel/message/109808 Mute This Topic: https://groups.io/mt/102044004/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/leave/9847357/21656/1706620634/xyzzy [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
