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Commit b891fa50 authored by Eric Ren's avatar Eric Ren Committed by Linus Torvalds
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ocfs2: fix deadlock issue when taking inode lock at vfs entry points 

Commit 743b5f14 ("ocfs2: take inode lock in ocfs2_iop_set/get_acl()")
results in a deadlock, as the author "Tariq Saeed" realized shortly
after the patch was merged.  The discussion happened here

  https://oss.oracle.com/pipermail/ocfs2-devel/2015-September/011085.html

The reason why taking cluster inode lock at vfs entry points opens up a
self deadlock window, is explained in the previous patch of this series.

So far, we have seen two different code paths that have this issue.

1. do_sys_open
     may_open
      inode_permission
       ocfs2_permission
        ocfs2_inode_lock() <=== take PR
         generic_permission
          get_acl
           ocfs2_iop_get_acl
            ocfs2_inode_lock() <=== take PR

2. fchmod|fchmodat
    chmod_common
     notify_change
      ocfs2_setattr <=== take EX
       posix_acl_chmod
        get_acl
         ocfs2_iop_get_acl <=== take PR
        ocfs2_iop_set_acl <=== take EX

Fixes them by adding the tracking logic (in the previous patch) for these
funcs above, ocfs2_permission(), ocfs2_iop_[set|get]_acl(),
ocfs2_setattr().

Link: http://lkml.kernel.org/r/20170117100948.11657-3-zren@suse.com


Signed-off-by: default avatarEric Ren <zren@suse.com>
Reviewed-by: default avatarJunxiao Bi <junxiao.bi@oracle.com>
Reviewed-by: default avatarJoseph Qi <jiangqi903@gmail.com>
Cc: Mark Fasheh <mfasheh@versity.com>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 439a36b8

fs/ocfs2/acl.c

+13 −16
Original line number Diff line number Diff line
@@ -283,16 +283,14 @@ int ocfs2_set_acl(handle_t *handle, 
int ocfs2_iop_set_acl(struct inode *inode, struct posix_acl *acl, int type)

{

	struct buffer_head *bh = NULL;

	int status = 0;

	int status, had_lock;

	struct ocfs2_lock_holder oh;



	status = ocfs2_inode_lock(inode, &bh, 1);

	if (status < 0) {

		if (status != -ENOENT)

			mlog_errno(status);

		return status;

	}

	had_lock = ocfs2_inode_lock_tracker(inode, &bh, 1, &oh);

	if (had_lock < 0)

		return had_lock;

	status = ocfs2_set_acl(NULL, inode, bh, type, acl, NULL, NULL);

	ocfs2_inode_unlock(inode, 1);

	ocfs2_inode_unlock_tracker(inode, 1, &oh, had_lock);

	brelse(bh);

	return status;

}
@@ -302,21 +300,20 @@ struct posix_acl *ocfs2_iop_get_acl(struct inode *inode, int type) 
	struct ocfs2_super *osb;

	struct buffer_head *di_bh = NULL;

	struct posix_acl *acl;

	int ret;

	int had_lock;

	struct ocfs2_lock_holder oh;



	osb = OCFS2_SB(inode->i_sb);

	if (!(osb->s_mount_opt & OCFS2_MOUNT_POSIX_ACL))

		return NULL;

	ret = ocfs2_inode_lock(inode, &di_bh, 0);

	if (ret < 0) {

		if (ret != -ENOENT)

			mlog_errno(ret);

		return ERR_PTR(ret);

	}



	had_lock = ocfs2_inode_lock_tracker(inode, &di_bh, 0, &oh);

	if (had_lock < 0)

		return ERR_PTR(had_lock);



	acl = ocfs2_get_acl_nolock(inode, type, di_bh);



	ocfs2_inode_unlock(inode, 0);

	ocfs2_inode_unlock_tracker(inode, 0, &oh, had_lock);

	brelse(di_bh);

	return acl;

}

fs/ocfs2/file.c

+45 −13
Original line number Diff line number Diff line
@@ -1138,6 +1138,8 @@ int ocfs2_setattr(struct dentry *dentry, struct iattr *attr) 
	handle_t *handle = NULL;

	struct dquot *transfer_to[MAXQUOTAS] = { };

	int qtype;

	int had_lock;

	struct ocfs2_lock_holder oh;



	trace_ocfs2_setattr(inode, dentry,

			    (unsigned long long)OCFS2_I(inode)->ip_blkno,
@@ -1173,11 +1175,30 @@ int ocfs2_setattr(struct dentry *dentry, struct iattr *attr) 
		}

	}



	status = ocfs2_inode_lock(inode, &bh, 1);

	if (status < 0) {

		if (status != -ENOENT)

			mlog_errno(status);

	had_lock = ocfs2_inode_lock_tracker(inode, &bh, 1, &oh);

	if (had_lock < 0) {

		status = had_lock;

		goto bail_unlock_rw;

	} else if (had_lock) {

		/*

		 * As far as we know, ocfs2_setattr() could only be the first

		 * VFS entry point in the call chain of recursive cluster

		 * locking issue.

		 *

		 * For instance:

		 * chmod_common()

		 *  notify_change()

		 *   ocfs2_setattr()

		 *    posix_acl_chmod()

		 *     ocfs2_iop_get_acl()

		 *

		 * But, we're not 100% sure if it's always true, because the

		 * ordering of the VFS entry points in the call chain is out

		 * of our control. So, we'd better dump the stack here to

		 * catch the other cases of recursive locking.

		 */

		mlog(ML_ERROR, "Another case of recursive locking:\n");

		dump_stack();

	}

	inode_locked = 1;
@@ -1260,8 +1281,8 @@ int ocfs2_setattr(struct dentry *dentry, struct iattr *attr) 
bail_commit:

	ocfs2_commit_trans(osb, handle);

bail_unlock:

	if (status) {

		ocfs2_inode_unlock(inode, 1);

	if (status && inode_locked) {

		ocfs2_inode_unlock_tracker(inode, 1, &oh, had_lock);

		inode_locked = 0;

	}

bail_unlock_rw:
@@ -1279,7 +1300,7 @@ int ocfs2_setattr(struct dentry *dentry, struct iattr *attr) 
			mlog_errno(status);

	}

	if (inode_locked)

		ocfs2_inode_unlock(inode, 1);

		ocfs2_inode_unlock_tracker(inode, 1, &oh, had_lock);



	brelse(bh);

	return status;
@@ -1320,21 +1341,32 @@ int ocfs2_getattr(struct vfsmount *mnt, 


int ocfs2_permission(struct inode *inode, int mask)

{

	int ret;

	int ret, had_lock;

	struct ocfs2_lock_holder oh;



	if (mask & MAY_NOT_BLOCK)

		return -ECHILD;



	ret = ocfs2_inode_lock(inode, NULL, 0);

	if (ret) {

		if (ret != -ENOENT)

			mlog_errno(ret);

	had_lock = ocfs2_inode_lock_tracker(inode, NULL, 0, &oh);

	if (had_lock < 0) {

		ret = had_lock;

		goto out;

	} else if (had_lock) {

		/* See comments in ocfs2_setattr() for details.

		 * The call chain of this case could be:

		 * do_sys_open()

		 *  may_open()

		 *   inode_permission()

		 *    ocfs2_permission()

		 *     ocfs2_iop_get_acl()

		 */

		mlog(ML_ERROR, "Another case of recursive locking:\n");

		dump_stack();

	}



	ret = generic_permission(inode, mask);



	ocfs2_inode_unlock(inode, 0);

	ocfs2_inode_unlock_tracker(inode, 0, &oh, had_lock);

out:

	return ret;

}