From e079d7c4db5cba1e8a315dc93030dfb6c7b49459 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Wed, 23 Apr 2025 06:59:41 +0200 Subject: [PATCH] devtmpfs: don't use vfs_getattr_nosec to query i_mode The recent move of the bdev_statx call to the low-level vfs_getattr_nosec helper caused it being used by devtmpfs, which leads to deadlocks in md teardown due to the block device lookup and put interfering with the unusual lifetime rules in md. But as handle_remove only works on inodes created and owned by devtmpfs itself there is no need to use vfs_getattr_nosec vs simply reading the mode from the inode directly. Switch to that to avoid the bdev lookup or any other unintentional side effect. Reported-by: Shin'ichiro Kawasaki Reported-by: Xiao Ni Fixes: 777d0961ff95 ("fs: move the bdex_statx call to vfs_getattr_nosec") Signed-off-by: Christoph Hellwig Link: https://lore.kernel.org/20250423045941.1667425-1-hch@lst.de Tested-by: Shin'ichiro Kawasaki Tested-by: Xiao Ni Tested-by: Ayush Jain Tested-by: Heiko Carstens Reviewed-by: Christian Brauner Signed-off-by: Christian Brauner --- drivers/base/devtmpfs.c | 22 +++++++++------------- 1 file changed, 9 insertions(+), 13 deletions(-) diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c index 6dd1a8860f1c..31bfb3194b4c 100644 --- a/drivers/base/devtmpfs.c +++ b/drivers/base/devtmpfs.c @@ -296,7 +296,7 @@ static int delete_path(const char *nodepath) return err; } -static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat) +static int dev_mynode(struct device *dev, struct inode *inode) { /* did we create it */ if (inode->i_private != &thread) @@ -304,13 +304,13 @@ static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *sta /* does the dev_t match */ if (is_blockdev(dev)) { - if (!S_ISBLK(stat->mode)) + if (!S_ISBLK(inode->i_mode)) return 0; } else { - if (!S_ISCHR(stat->mode)) + if (!S_ISCHR(inode->i_mode)) return 0; } - if (stat->rdev != dev->devt) + if (inode->i_rdev != dev->devt) return 0; /* ours */ @@ -321,20 +321,16 @@ static int handle_remove(const char *nodename, struct device *dev) { struct path parent; struct dentry *dentry; - struct kstat stat; - struct path p; + struct inode *inode; int deleted = 0; - int err; + int err = 0; dentry = kern_path_locked(nodename, &parent); if (IS_ERR(dentry)) return PTR_ERR(dentry); - p.mnt = parent.mnt; - p.dentry = dentry; - err = vfs_getattr(&p, &stat, STATX_TYPE | STATX_MODE, - AT_STATX_SYNC_AS_STAT); - if (!err && dev_mynode(dev, d_inode(dentry), &stat)) { + inode = d_inode(dentry); + if (dev_mynode(dev, inode)) { struct iattr newattrs; /* * before unlinking this node, reset permissions @@ -342,7 +338,7 @@ static int handle_remove(const char *nodename, struct device *dev) */ newattrs.ia_uid = GLOBAL_ROOT_UID; newattrs.ia_gid = GLOBAL_ROOT_GID; - newattrs.ia_mode = stat.mode & ~0777; + newattrs.ia_mode = inode->i_mode & ~0777; newattrs.ia_valid = ATTR_UID|ATTR_GID|ATTR_MODE; inode_lock(d_inode(dentry));