Re: [PATCH 0/5] MdeModulePkg: UDF fixes and cleanups

["Shi, Steven" <steven.shi@intel.com>]

Hi Laszlo,
Your code is good. But there is a "Null Pointer Use" issue, which is a undefined behavior in C spec, in edk2/MdeModulePkg/Universal/Disk/UdfDxe/File.c, line:696, column: 7 and line:707, column: 14.

Line695:
  FileIdentifierDesc = PrivFileData->File.FileIdentifierDesc;
  if (IS_FID_DIRECTORY_FILE (FileIdentifierDesc)) {
   ...

The above FileIdentifierDesc can be NULL if you run a .efi in a Udf partition. And the later IS_FID_DIRECTORY_FILE (FileIdentifierDesc) is unsafe if FileIdentifierDesc == NULL. You can test it with below extra code which add debug output when FileIdentifierDesc == NULL, and check the log after load and run something in a Udf partition.

+++ b/MdeModulePkg/Universal/Disk/UdfDxe/File.c
@@ -693,6 +693,11 @@ UdfSetPosition (
   PrivFileData = PRIVATE_UDF_FILE_DATA_FROM_THIS (This);

   FileIdentifierDesc = PrivFileData->File.FileIdentifierDesc;
+  if (FileIdentifierDesc == NULL) {
+    DEBUG ((EFI_D_ERROR, "FileIdentifierDesc == NULL!\n"));
+    return Status;
+  }
+
   if (IS_FID_DIRECTORY_FILE (FileIdentifierDesc)) {
     //
     // If the file handle is a directory, the _only_ position that may be set is

I followed the Paulo's suggestion, and found this issue when using the Udf partition of Windows 10 Enterprise ISO image on qemu. Below is my qemu command:
/usr/local/bin/qemu-system-x86_64 -m 5120 -enable-kvm  -machine pc-q35-2.9 -bios OVMF.fd -serial file:serial.log  -cdrom /media/jshi19/My\ Passport/OSImage/ISO/winserver/en_windows_server_2016_x64_dvd_9327751.iso

I've submitted a bug for this issue: https://bugzilla.tianocore.org/show_bug.cgi?id=704. 

I found this issue by edk2 llvm undefined behavior sanitizer, and below is the sanitizer output. FYI.
/home/jshi19/wksp_efi/edk2/MdeModulePkg/Universal/Disk/UdfDxe/File.c, line:0x02B8, column:0x0007 ErrorType = NullPointerUse: member access within null pointer of type 'UDF_FILE_IDENTIFIER_DESCRIPTOR'
ASAN MEMORY ACCESS check fail! __ubsan_handle_type_mismatch_v1 is called: 
UdfSetPosition
/home/jshi19/wksp_efi/edk2/MdeModulePkg/Universal/Disk/UdfDxe/File.c:696:7
EfiShellFindFilesInDir
/home/jshi19/wksp_efi/edk2/ShellPkg/Application/Shell/ShellProtocol.c:2136:18
ShellSearchHandle
/home/jshi19/wksp_efi/edk2/ShellPkg/Application/Shell/ShellProtocol.c:2413:14
EfiShellFindFiles
/home/jshi19/wksp_efi/edk2/ShellPkg/Application/Shell/ShellProtocol.c:2586:18
EfiShellOpenFileList
/home/jshi19/wksp_efi/edk2/ShellPkg/Application/Shell/ShellProtocol.c:2666:12
ShellOpenFileMetaArg
/home/jshi19/wksp_efi/edk2/ShellPkg/Library/UefiShellLib/UefiShellLib.c:1570:14

/home/jshi19/wksp_efi/edk2/MdeModulePkg/Universal/Disk/UdfDxe/File.c, line:0x02C3, column:0x000E ErrorType = NullPointerUse: member access within null pointer of type 'UDF_FILE_IDENTIFIER_DESCRIPTOR'
ASAN MEMORY ACCESS check fail! __ubsan_handle_type_mismatch_v1 is called:
...

Steven Shi
Intel\SSG\STO\UEFI Firmware

Tel: +86 021-61166522
iNet: 821-6522

> -----Original Message-----
> From: Paulo Alcantara [mailto:pcacjr@zytor.com]
> Sent: Sunday, September 10, 2017 11:52 PM
> To: Shi, Steven <steven.shi@intel.com>; Laszlo Ersek <lersek@redhat.com>;
> edk2-devel-01 <edk2-devel@lists.01.org>
> Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Dong, Eric <eric.dong@intel.com>; Zeng,
> Star <star.zeng@intel.com>; Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Subject: Re: [edk2] [PATCH 0/5] MdeModulePkg: UDF fixes and cleanups
> 
> 
> 
> On 10/09/2017 11:27, Shi, Steven wrote:
> > OK. Does the UDF image you created correctly show up as CD-ROM
> content in Linux, e.g Fedora?
> 
> The Fedora image I have (Fedora-Workstation-Live-x86_64-26-1.5.iso) does
> not contain a valid UDF file system, so you cannot use it for testing.
> 
> To make sure it really doesn't, I used a "Philips UDF Conformance Tool"
> that you can grab in [1], and the tool didn't find any valid UDF file
> system in it.
> 
> I've been using an unmodified Windows 10 Enterprise image that does
> contain a valid UDF bridge disk image (ISO9660+ElTorito+UDF) to perform
> my tests.
> 
> Additionally, I use an USB stick that I format it with 'sudo mkudffs -b
> 512 --media-type=hd /dev/sdX' and copy some files to it for testing
> 
> BTW, when testing with OVMF AARCH64, I was using my USB stick that
> showed up correctly as 'fsX' in UEFI shell, but with the Windows 10
> Enterprise ISO image, it didn't. I looked at the logs to see what was
> going on and I found out that the emulated CD-ROM drive is reporting a
> block size of 512 instead of 2048 -- which seems wrong to me. With
> 'qemu-system-x86_64 -cdrom', it reports a block size of 2048.
> 
> The Partition driver is still able to find a valid ElTorito partition
> because, regardless the device block size, it always use a logical block
> size of 2048 starting at 32K. In UDF, when searching for AVDPs (Anchor
> Volume Descriptor Pointers), we search for them at fixed locations: 256,
> N - 256, N and 512 -- but, with a block size of 512, the locations
> change to 1024, N - 1024, N and 2048 -- thus breaking the volume
> recognition sequence.
> 
> For testing the Windows image with a block size of 512, I used the
> comformance tool with './udf_test -verbose 60 -blocksize 512
> ~/img/win_ent10.iso' and it failed to find a valid UDF file system. But
> with a block size of 2048, it worked.
> 
> Is there any reason for reporting a block size of 512 when using
> '-cdrom' option in qemu-system-aarch64? Is that a bug? Or am I missing
> something here?
> 
> Thanks!
> Paulo
> 
> [1] - https://www.lscdweb.com/registered/udf_verifier.html
> 
> >
> >
> > Steven Shi
> > Intel\SSG\STO\UEFI Firmware
> >
> > Tel: +86 021-61166522
> > iNet: 821-6522
> >
> >> -----Original Message-----
> >> From: Laszlo Ersek [mailto:lersek@redhat.com]
> >> Sent: Sunday, September 10, 2017 9:52 PM
> >> To: Shi, Steven <steven.shi@intel.com>; edk2-devel-01 <edk2-
> >> devel@lists.01.org>
> >> Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Dong, Eric <eric.dong@intel.com>;
> Zeng,
> >> Star <star.zeng@intel.com>; Ard Biesheuvel <ard.biesheuvel@linaro.org>
> >> Subject: Re: [edk2] [PATCH 0/5] MdeModulePkg: UDF fixes and cleanups
> >>
> >> Hi Steven,
> >>
> >> On 09/10/17 10:38, Laszlo Ersek wrote:
> >>> On 09/10/17 06:24, Shi, Steven wrote:
> >>>> Hi Laszlo,
> >>>> How could we configure the Qemu and test the UDF driver on OVMF?
> >>>
> >>> I guess you would format e.g. a DVD image with UDF, and attach it to
> >>> QEMU like any other CD-ROM.
> >>
> >> I tried to look into this -- I tried several things, but nothing
> >> produced an UDF image file that, when attached to the VM, would show
> up
> >> in the UEFI shell as FSn:
> >>
> >> Google returned a bunch of pages, but all I found was:
> >> - tips that didn't work (see above),
> >> - confused users (like me) looking for solutions.
> >>
> >> So, at the moment, I have no idea how authoring UDF DVD images is
> >> possible on Linux, so that they'd be recognized in edk2.
> >>
> >> (I'm interested in the edk2 UDF driver not because I want to "author"
> >> UDF DVD images (ISO9660+ElTorito works just fine), but because some
> >> optical media images that were given to me are formatted UDF-only.
> They
> >> can be translated into ISO9660+ElTorito off-line, but that's a chore.)
> >>
> >> Thanks,
> >> Laszlo
> > _______________________________________________
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> > edk2-devel@lists.01.org
> > https://lists.01.org/mailman/listinfo/edk2-devel
> >