Patch "gfs2: Silence "suspicious RCU usage in gfs2_permission" warning" has been added to the 6.6-stable tree

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This is a note to let you know that I've just added the patch titled

    gfs2: Silence "suspicious RCU usage in gfs2_permission" warning

to the 6.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     gfs2-silence-suspicious-rcu-usage-in-gfs2_permission.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 22bfd6a4a66458eef633efa2d60760f19c8d8b23
Author: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
Date:   Mon Oct 30 22:06:05 2023 +0100

    gfs2: Silence "suspicious RCU usage in gfs2_permission" warning
    
    [ Upstream commit 074d7306a4fe22fcac0b53f699f92757ab1cee99 ]
    
    Commit 0abd1557e21c added rcu_dereference() for dereferencing ip->i_gl
    in gfs2_permission.  This now causes lockdep to complain when
    gfs2_permission is called in non-RCU context:
    
        WARNING: suspicious RCU usage in gfs2_permission
    
    Switch to rcu_dereference_check() and check for the MAY_NOT_BLOCK flag
    to shut up lockdep when we know that dereferencing ip->i_gl is safe.
    
    Fixes: 0abd1557e21c ("gfs2: fix an oops in gfs2_permission")
    Reported-by: syzbot+3e5130844b0c0e2b4948@xxxxxxxxxxxxxxxxxxxxxxxxx
    Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index eb4bbe1728c06..4e63fbb63151c 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -1866,6 +1866,7 @@ static const char *gfs2_get_link(struct dentry *dentry,
 int gfs2_permission(struct mnt_idmap *idmap, struct inode *inode,
 		    int mask)
 {
+	int may_not_block = mask & MAY_NOT_BLOCK;
 	struct gfs2_inode *ip;
 	struct gfs2_holder i_gh;
 	struct gfs2_glock *gl;
@@ -1873,14 +1874,14 @@ int gfs2_permission(struct mnt_idmap *idmap, struct inode *inode,
 
 	gfs2_holder_mark_uninitialized(&i_gh);
 	ip = GFS2_I(inode);
-	gl = rcu_dereference(ip->i_gl);
+	gl = rcu_dereference_check(ip->i_gl, !may_not_block);
 	if (unlikely(!gl)) {
 		/* inode is getting torn down, must be RCU mode */
-		WARN_ON_ONCE(!(mask & MAY_NOT_BLOCK));
+		WARN_ON_ONCE(!may_not_block);
 		return -ECHILD;
         }
 	if (gfs2_glock_is_locked_by_me(gl) == NULL) {
-		if (mask & MAY_NOT_BLOCK)
+		if (may_not_block)
 			return -ECHILD;
 		error = gfs2_glock_nq_init(gl, LM_ST_SHARED, LM_FLAG_ANY, &i_gh);
 		if (error)



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