From: Al Viro viro@zeniv.linux.org.uk
stable inclusion from stable-v6.6.3 commit 7f9b5e974cbb500ea88643b385913ab41cc6560b category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I8LBQP
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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[ Upstream commit 0abd1557e21c617bd13fc18f7725fc6363c05913 ]
In RCU mode, we might race with gfs2_evict_inode(), which zeroes ->i_gl. Freeing of the object it points to is RCU-delayed, so if we manage to fetch the pointer before it's been replaced with NULL, we are fine. Check if we'd fetched NULL and treat that as "bail out and tell the caller to get out of RCU mode".
Signed-off-by: Al Viro viro@zeniv.linux.org.uk Signed-off-by: Andreas Gruenbacher agruenba@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- fs/gfs2/inode.c | 11 +++++++++-- fs/gfs2/super.c | 2 +- 2 files changed, 10 insertions(+), 3 deletions(-)
diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c index 0eac04507904..eb4bbe1728c0 100644 --- a/fs/gfs2/inode.c +++ b/fs/gfs2/inode.c @@ -1868,14 +1868,21 @@ int gfs2_permission(struct mnt_idmap *idmap, struct inode *inode, { struct gfs2_inode *ip; struct gfs2_holder i_gh; + struct gfs2_glock *gl; int error;
gfs2_holder_mark_uninitialized(&i_gh); ip = GFS2_I(inode); - if (gfs2_glock_is_locked_by_me(ip->i_gl) == NULL) { + gl = rcu_dereference(ip->i_gl); + if (unlikely(!gl)) { + /* inode is getting torn down, must be RCU mode */ + WARN_ON_ONCE(!(mask & MAY_NOT_BLOCK)); + return -ECHILD; + } + if (gfs2_glock_is_locked_by_me(gl) == NULL) { if (mask & MAY_NOT_BLOCK) return -ECHILD; - error = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, LM_FLAG_ANY, &i_gh); + error = gfs2_glock_nq_init(gl, LM_ST_SHARED, LM_FLAG_ANY, &i_gh); if (error) return error; } diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c index 02d93da21b2b..0dd5641990b9 100644 --- a/fs/gfs2/super.c +++ b/fs/gfs2/super.c @@ -1550,7 +1550,7 @@ static void gfs2_evict_inode(struct inode *inode) wait_on_bit_io(&ip->i_flags, GIF_GLOP_PENDING, TASK_UNINTERRUPTIBLE); gfs2_glock_add_to_lru(ip->i_gl); gfs2_glock_put_eventually(ip->i_gl); - ip->i_gl = NULL; + rcu_assign_pointer(ip->i_gl, NULL); } }