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authorAlexey Dobriyan <adobriyan@gmail.com>2018-04-13 15:35:42 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-04-13 17:10:27 -0700
commit1da4d377f943fe4194ffb9fb9c26cc58fad4dd24 (patch)
treeaed9f3e163f7ecbe85351b92e32ba66a7301c97b
parenta9f2a846f0503e7d729f552e3ccfe2279010fe94 (diff)
downloadlinux-stericsson-1da4d377f943fe4194ffb9fb9c26cc58fad4dd24.tar.gz
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@gmail.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/proc/generic.c23
1 files changed, 22 insertions, 1 deletions
diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index 04c4804cbdef..2078e70e1595 100644
--- a/fs/proc/generic.c
+++ b/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 inode *dir, struct dentry *dentry,
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;
}