linux-kernel - Re: [RFC] setxattr bugs

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Message-ID: <51106AF1.4030804@suse.com>
Date:	Mon, 04 Feb 2013 21:14:09 -0500
From:	Jeff Mahoney <jeffm@...e.com>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-fsdevel@...r.kernel.org, Dave Kleikamp <shaggy@...nel.org>
Subject: Re: [RFC] setxattr bugs

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On 2/2/13 11:30 PM, Al Viro wrote:
> * JFS, since 2005: setxattr(name, "system.posix_acl_access", NULL,
> 0, 0) succeeds, creating an empty EA with "system.posix_acl_access"
> as name. Validity checks should apply _after_ if (value == NULL) {
> /* empty EA, do not remove */ value = ""; value_len = 0; } and not
> before it. * reiserfs, since 2009: setxattr(name, attr_name, NULL,
> 0, 0) is treated as removexattr(name, attr_name), not as emptying
> given xattr.
> 
> The question is, does either of those cross into "established 
> weirdness in ABI" or are they still at the "bugs to be fixed"
> stage?

Since the behavior changed once already in 2009 I'd call it a bug.
That code was in the SLES kernel for a while before then and I still
haven't seen a bug report on it.

- -Jeff

> FWIW, I'm seriously tempted to stop passing NULL as the third
> argument of ->setxattr(), essentially taking all those if (!value)
> value = ""; pieces from individual ->setxattr() instances to
> __vfs_setxattr_noperm() (all other callers of ->setxattr() never 
> pass NULL data or 0 size, so it's irrelevant for them).  Would fix 
> both jfs and reiserfs weirdness....
> 
> Objections?




- -- 
Jeff Mahoney
SUSE Labs
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