From: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Subject: proc: revalidate misc dentries
If module removes proc directory while another process pins it by
chdir'ing to it, then subsequent recreation of proc entry and all entries
down the tree will not be visible to any process until pinning process
unchdir from directory and unpins everything.
Steps to reproduce:
proc_mkdir("aaa", NULL);
proc_create("aaa/bbb", ...);
chdir("/proc/aaa");
remove_proc_entry("aaa/bbb", NULL);
remove_proc_entry("aaa", NULL);
proc_mkdir("aaa", NULL);
# inaccessible because "aaa" dentry still points
# to the original "aaa".
proc_create("aaa/bbb", ...);
Fix is to implement ->d_revalidate and ->d_delete.
Link: http://lkml.kernel.org/r/20180312201938.GA4871@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/generic.c | 23 ++++++++++++++++++++++-
1 file changed, 22 insertions(+), 1 deletion(-)
diff -puN fs/proc/generic.c~proc-revalidate-misc-dentries fs/proc/generic.c
--- a/fs/proc/generic.c~proc-revalidate-misc-dentries
+++ a/fs/proc/generic.c
@@ -15,6 +15,7 @@
#include <linux/stat.h>
#include <linux/mm.h>
#include <linux/module.h>
+#include <linux/namei.h>
#include <linux/slab.h>
#include <linux/printk.h>
#include <linux/mount.h>
@@ -217,6 +218,26 @@ void proc_free_inum(unsigned int inum)
ida_simple_remove(&proc_inum_ida, inum - PROC_DYNAMIC_FIRST);
}
+static int proc_misc_d_revalidate(struct dentry *dentry, unsigned int flags)
+{
+ if (flags & LOOKUP_RCU)
+ return -ECHILD;
+
+ if (atomic_read(&PDE(d_inode(dentry))->in_use) < 0)
+ return 0; /* revalidate */
+ return 1;
+}
+
+static int proc_misc_d_delete(const struct dentry *dentry)
+{
+ return atomic_read(&PDE(d_inode(dentry))->in_use) < 0;
+}
+
+static const struct dentry_operations proc_misc_dentry_ops = {
+ .d_revalidate = proc_misc_d_revalidate,
+ .d_delete = proc_misc_d_delete,
+};
+
/*
* Don't create negative dentries here, return -ENOENT by hand
* instead.
@@ -234,7 +255,7 @@ struct dentry *proc_lookup_de(struct ino
inode = proc_get_inode(dir->i_sb, de);
if (!inode)
return ERR_PTR(-ENOMEM);
- d_set_d_op(dentry, &simple_dentry_operations);
+ d_set_d_op(dentry, &proc_misc_dentry_ops);
d_add(dentry, inode);
return NULL;
}
_
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
