5.15-stable review patch. If anyone has any objections, please let me know.
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From: Andreas Gruenbacher agruenba@redhat.com
[ 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@syzkaller.appspotmail.com Signed-off-by: Andreas Gruenbacher agruenba@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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)