5.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
[ 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>
---
fs/gfs2/inode.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index 682418d9c8e72..462e957eda8be 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -1848,6 +1848,7 @@ static const char *gfs2_get_link(struct dentry *dentry,
int gfs2_permission(struct user_namespace *mnt_userns, 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;
@@ -1855,14 +1856,14 @@ int gfs2_permission(struct user_namespace *mnt_userns, 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)
--
2.42.0
