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RE: [edk2] Should Path Name in File Path Media Device Path node be NULL


From: Tian, Feng
Subject: RE: [edk2] Should Path Name in File Path Media Device Path node be NULL terminated?
Date: Fri, 24 Feb 2017 07:40:09 +0000

UEFI spec clearly say:

"Path Name" is A NULL-terminated Path string including directory and file 
names. The length of this string n can be determined by
subtracting 4 from the Length entry. A device path may contain one or more of 
these nodes. Each node can optionally add a "\" separator to the beginning 
and/or the end of the Path Name string. The complete path to a file can be 
found by logically concatenating all the Path Name strings in the File Path 
Media Device Path nodes. This is typically used to describe the directory path 
in one node, and the filename in another node.

Thanks
Feng

-----Original Message-----
From: edk2-devel [mailto:address@hidden On Behalf Of Andrei Borzenkov
Sent: Friday, February 24, 2017 3:06 PM
To: edk2-devel-01 <address@hidden>; The development of GNU GRUB <address@hidden>
Subject: [edk2] Should Path Name in File Path Media Device Path node be NULL 
terminated?

Historically grub2 built image paths using two File Path nodes - one for 
directory and one for file name relative to directory. These nodes had path 
names that were not NULL terminated.

Recently we had bug report that secure boot using grub2 failed. It was tracked 
down to exactly the fact that paths were not NULL terminated.
See
http://git.savannah.gnu.org/cgit/grub.git/commit/?id=ce95549cc54b5d6f494608a7c390dba3aab4fba7

Unfortunately this caused another regression which looks like firmware 
truncating passed image path on first NULL

https://bugzilla.opensuse.org/show_bug.cgi?id=1026344

Could someone clarify what is expected by EFI spec? Should each Path Name (even 
intermediate) be NULL terminated, or spec intends to say that only full path 
must be NULL terminated?
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