lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Sun, 21 Oct 2018 08:30:35 +0300
From:   Amir Goldstein <>
To:     Matthew Wilcox <>
Cc:, Evgeniy Dushistov <>,
        Al Viro <>,,
        linux-kernel <>,
        linux-fsdevel <>
Subject: Re: [PATCH] fs: ufs: Remove switch statement from ufs_set_de_type function

On Sun, Oct 21, 2018 at 1:27 AM Matthew Wilcox <> wrote:
> On Sat, Oct 20, 2018 at 11:09:57PM +0100, Phillip Potter wrote:
> > Remove switch statement from ufs_set_de_type function in fs/ufs/util.h
> > header and replace with simple assignment. For each case, S_IFx >> 12
> > is equal to DT_x, so in valid cases (mode & S_IFMT) >> 12 should give
> > us the correct file type. It is expected that for *nix compatibility
> > reasons, the relation between S_IFx and DT_x will not change. For
> > cases where the mode is invalid, upper layer validation catches this
> > anyway, so this improves readability and arguably performance by
> > assigning (mode & S_IFMT) >> 12 directly without any jump table
> > or conditional logic.
> Shouldn't we also do this for other filesystems?  A quick scan suggests
> someone should at least look at xfs, ubifs, squashfs, romfs, ocfs2,
> nilfs2, hfsplus, f2fs, ext4, ext2, exofs, coda, cifs & btrfs.

I've tried to do that 2 years ago, not even for readability, but to
fix a lurking
bug in conversion table implementation that was copy&pasted from ext2 to
many other fs:

The push back from ext4/xfs maintainers was that while all fs use common
values to encode d_type in on disk format, those on-disk format values
are private to the fs.

Eventually, the fix that got merged (only to xfs) did the opposite, it converted
the conversion table lookup to a switch statement:

Some fs maintainers were happy about the initial version, but I did not
pursue pushing that cleanup:

Phillip, you are welcome to re-spin those patches if you like.
Note that the generic conversion helpers do not rely on upper layer
to catch invalid mode values.


Powered by blists - more mailing lists