Messages in this thread | | | Date | Mon, 10 Sep 2018 17:16:08 -0600 (Mountain Daylight Time) | From | Marc Aurèle La France <> | Subject | Re: sysfs: Do not return POSIX ACL xattrs via listxattr() |
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On Mon, 10 Sep 2018, Andreas Grünbacher wrote: > Am Mo., 10. Sep. 2018 schrieb Marc Aurèle La France:
>> Commit 786534b92f3ce68f4afc8a761c80b76887797b0a "tmpfs: listxattr >> should include POSIX ACL xattrs", which first appeared in 4.5 kernels, >> introduced a regression whereby listxattr() syscalls on anything in >> sysfs, or its mountpoint, return the name of the two POSIX ACL xattrs, >> but attempts to retrieve these values are denied with EOPNOTSUP. For >> example ...
>> # getfattr -d --match=- /sys >> /sys: system.posix_acl_access: Operation not supported >> /sys: system.posix_acl_default: Operation not supported >> #
> I can confirm this regression.
>> This inconsistent behaviour confuses rsync(1) (among others) when it >> runs into a sysfs mountpoint, even when told to not descend into it. >> This issue occurs because simple_xattr_list() does not correctly deal >> with cached ACLs.
>> The suggested fix below was developed with a 4.18.7 kernel, but should >> apply, modulo patch fuzz, to any kernel >= 4.7. A fix for 4.5 <= >> kernels < 4.7 is trivially different, but I won't bother given such >> kernels are no longer maintained.
>> Note that the only other simple_xattr_list() caller, shmem, avoids >> this glitch by previously calling cache_no_acl() on all inodes it >> creates, so perhaps sysfs/kernfs should do the same.
>> Signed-off-by: Marc Aurèle La France <tsi@tuyoix.net>
>> --- a/fs/xattr.c >> +++ b/fs/xattr.c >> @@ -949,13 +949,13 @@ ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs, >> int err = 0; >> >> #ifdef CONFIG_FS_POSIX_ACL >> - if (inode->i_acl) { >> + if (inode->i_acl && !is_uncached_acl(inode->i_acl)) { >> err = xattr_list_one(&buffer, &remaining_size, >> XATTR_NAME_POSIX_ACL_ACCESS); >> if (err) >> return err; >> } >> - if (inode->i_default_acl) { >> + if (inode->i_default_acl && !is_uncached_acl(inode->i_default_acl)) { >> err = xattr_list_one(&buffer, &remaining_size, >> XATTR_NAME_POSIX_ACL_DEFAULT); >> if (err)
> This seems to be a better fix, but I haven't fully verified it, yet:
> --- a/fs/inode.c > +++ b/fs/inode.c > @@ -187,7 +187,8 @@ int inode_init_always(struct super_block *sb, struct > inode->i_mapping = mapping; > INIT_HLIST_HEAD(&inode->i_dentry); /* buggered by rcu freeing */ > #ifdef CONFIG_FS_POSIX_ACL > - inode->i_acl = inode->i_default_acl = ACL_NOT_CACHED; > + inode->i_acl = inode->i_default_acl = > + (sb->s_flags & SB_POSIXACL) ? ACL_NOT_CACHED : NULL; > #endif > > #ifdef CONFIG_FSNOTIFY
Yes, that works too, and doesn't seem to cause other issues.
Tested-by: Marc Aurèle La France <tsi@tuyoix.net>
Thanks.
Marc. | |