fs: Avoid premature clearing of capabilities

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commit 030b533c4f upstream.

Currently, notify_change() clears capabilities or IMA attributes by
calling security_inode_killpriv() before calling into ->setattr. Thus it
happens before any other permission checks in inode_change_ok() and user
is thus allowed to trigger clearing of capabilities or IMA attributes
for any file he can look up e.g. by calling chown for that file. This is
unexpected and can lead to user DoSing a system.

Fix the problem by calling security_inode_killpriv() at the end of
inode_change_ok() instead of from notify_change(). At that moment we are
sure user has permissions to do the requested change.

References: CVE-2015-1350
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

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Jan Kara 2016-05-26 17:21:32 +02:00 • committed by Ben Hutchings

parent be9df69943

commit 3418703a9d

1 changed files with 14 additions and 6 deletions

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fs/attr.c

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