66 lines
2.4 KiB
Diff
66 lines
2.4 KiB
Diff
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From linux-fsdevel-owner@vger.kernel.org Thu Nov 18 21:03:11 2010
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From: Josef Bacik <josef@redhat.com>
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To: linux-fsdevel@vger.kernel.org, eparis@redhat.com,
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linux-kernel@vger.kernel.org, sds@tycho.nsa.gov,
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selinux@tycho.nsa.gov, bfields@fieldses.org
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Subject: [PATCH] fs: call security_d_instantiate in d_obtain_alias V2
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Date: Thu, 18 Nov 2010 20:52:55 -0500
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Message-Id: <1290131575-2489-1-git-send-email-josef@redhat.com>
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X-Mailing-List: linux-fsdevel@vger.kernel.org
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While trying to track down some NFS problems with BTRFS, I kept noticing I was
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getting -EACCESS for no apparent reason. Eric Paris and printk() helped me
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figure out that it was SELinux that was giving me grief, with the following
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denial
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type=AVC msg=audit(1290013638.413:95): avc: denied { 0x800000 } for pid=1772
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comm="nfsd" name="" dev=sda1 ino=256 scontext=system_u:system_r:kernel_t:s0
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tcontext=system_u:object_r:unlabeled_t:s0 tclass=file
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Turns out this is because in d_obtain_alias if we can't find an alias we create
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one and do all the normal instantiation stuff, but we don't do the
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security_d_instantiate.
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Usually we are protected from getting a hashed dentry that hasn't yet run
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security_d_instantiate() by the parent's i_mutex, but obviously this isn't an
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option there, so in order to deal with the case that a second thread comes in
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and finds our new dentry before we get to run security_d_instantiate(), we go
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ahead and call it if we find a dentry already. Eric assures me that this is ok
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as the code checks to see if the dentry has been initialized already so calling
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security_d_instantiate() against the same dentry multiple times is ok. With
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this patch I'm no longer getting errant -EACCESS values.
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Signed-off-by: Josef Bacik <josef@redhat.com>
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---
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V1->V2:
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-added second security_d_instantiate() call
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fs/dcache.c | 3 +++
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1 files changed, 3 insertions(+), 0 deletions(-)
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diff --git a/fs/dcache.c b/fs/dcache.c
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index 23702a9..119d489 100644
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--- a/fs/dcache.c
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+++ b/fs/dcache.c
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@@ -1201,9 +1201,12 @@ struct dentry *d_obtain_alias(struct inode *inode)
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spin_unlock(&tmp->d_lock);
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spin_unlock(&dcache_lock);
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+ security_d_instantiate(tmp, inode);
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return tmp;
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out_iput:
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+ if (res && !IS_ERR(res))
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+ security_d_instantiate(res, inode);
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iput(inode);
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return res;
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}
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--
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1.6.6.1
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--
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