* [RFC] setxattr bugs
@ 2013-02-03 4:30 Al Viro
2013-02-03 13:59 ` Dave Kleikamp
2013-02-05 2:14 ` Jeff Mahoney
0 siblings, 2 replies; 4+ messages in thread
From: Al Viro @ 2013-02-03 4:30 UTC (permalink / raw)
To: linux-kernel; +Cc: Linus Torvalds, linux-fsdevel, Jeff Mahoney, Dave Kleikamp
* 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?
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?
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [RFC] setxattr bugs
2013-02-03 4:30 [RFC] setxattr bugs Al Viro
@ 2013-02-03 13:59 ` Dave Kleikamp
2013-02-05 2:14 ` Jeff Mahoney
1 sibling, 0 replies; 4+ messages in thread
From: Dave Kleikamp @ 2013-02-03 13:59 UTC (permalink / raw)
To: Al Viro
Cc: linux-kernel, Linus Torvalds, linux-fsdevel, Jeff Mahoney,
Dave Kleikamp
On 02/02/2013 10:30 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.
This is probably a hold-over from weird OS/2 behavior that we really
don't need to keep.
> * 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?
>
> 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?
no objection from me. I can clean up the jfs code so that it no longer
saves empty xattrs.
Thanks,
Shaggy
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [RFC] setxattr bugs
2013-02-03 4:30 [RFC] setxattr bugs Al Viro
2013-02-03 13:59 ` Dave Kleikamp
@ 2013-02-05 2:14 ` Jeff Mahoney
2013-02-05 17:14 ` Casey Schaufler
1 sibling, 1 reply; 4+ messages in thread
From: Jeff Mahoney @ 2013-02-05 2:14 UTC (permalink / raw)
To: Al Viro; +Cc: linux-kernel, Linus Torvalds, linux-fsdevel, Dave Kleikamp
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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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^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [RFC] setxattr bugs
2013-02-05 2:14 ` Jeff Mahoney
@ 2013-02-05 17:14 ` Casey Schaufler
0 siblings, 0 replies; 4+ messages in thread
From: Casey Schaufler @ 2013-02-05 17:14 UTC (permalink / raw)
To: Jeff Mahoney
Cc: Al Viro, linux-kernel, Linus Torvalds, linux-fsdevel,
Dave Kleikamp, LSM, Casey Schaufler
On 2/4/2013 6:14 PM, Jeff Mahoney wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> 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?
None from me. I know of no one using either of those filesystems
in ways I care about. There's a chance the SELinux crowd may care,
so I'm adding the LSM list. We're the primary consumer of xattrs.
>
> - --
> Jeff Mahoney
> SUSE Labs
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^ permalink raw reply [flat|nested] 4+ messages in thread
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2013-02-03 4:30 [RFC] setxattr bugs Al Viro
2013-02-03 13:59 ` Dave Kleikamp
2013-02-05 2:14 ` Jeff Mahoney
2013-02-05 17:14 ` Casey Schaufler
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