+ proc-sysctl-dont-return-enomem-on-lookup-when-a-table-is-unregistering.patch added to -mm tree

+ proc-sysctl-dont-return-enomem-on-lookup-when-a-table-is-unregistering.patch added to -mm tree

[akpm]

The patch titled
     Subject: proc/sysctl: don't return ENOMEM on lookup when a table is unregistering
has been added to the -mm tree.  Its filename is
     proc-sysctl-dont-return-enomem-on-lookup-when-a-table-is-unregistering.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/proc-sysctl-dont-return-enomem-on-lookup-when-a-table-is-unregistering.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/proc-sysctl-dont-return-enomem-on-lookup-when-a-table-is-unregistering.patch

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------------------------------------------------------
From: Ivan Delalande <colona@arista.com>
Subject: proc/sysctl: don't return ENOMEM on lookup when a table is unregistering

proc_sys_lookup can fail with ENOMEM instead of ENOENT when the
corresponding sysctl table is being unregistered.  In our case we see this
upon opening /proc/sys/net/*/conf files while network interfaces are being
deleted, which confuses our configuration daemon.

The problem was successfully reproduced and this fix tested on v4.9.122
and v4.20-rc6.

Link: http://lkml.kernel.org/r/20181213232052.GA1513@visor
Fixes: ace0c791e6c3 ("proc/sysctl: Don't grab i_lock under sysctl_lock.")
Signed-off-by: Ivan Delalande <colona@arista.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---


--- a/fs/proc/proc_sysctl.c~proc-sysctl-dont-return-enomem-on-lookup-when-a-table-is-unregistering
+++ a/fs/proc/proc_sysctl.c
@@ -464,7 +464,7 @@ static struct inode *proc_sys_make_inode
 
 	inode = new_inode(sb);
 	if (!inode)
-		goto out;
+		return ERR_PTR(-ENOMEM);
 
 	inode->i_ino = get_next_ino();
 
@@ -474,7 +474,7 @@ static struct inode *proc_sys_make_inode
 	if (unlikely(head->unregistering)) {
 		spin_unlock(&sysctl_lock);
 		iput(inode);
-		inode = NULL;
+		inode = ERR_PTR(-ENOENT);
 		goto out;
 	}
 	ei->sysctl = head;
@@ -549,10 +549,11 @@ static struct dentry *proc_sys_lookup(st
 			goto out;
 	}
 
-	err = ERR_PTR(-ENOMEM);
 	inode = proc_sys_make_inode(dir->i_sb, h ? h : head, p);
-	if (!inode)
+	if (IS_ERR(inode)) {
+		err = ERR_CAST(inode);
 		goto out;
+	}
 
 	d_set_d_op(dentry, &proc_sys_dentry_operations);
 	err = d_splice_alias(inode, dentry);
@@ -685,7 +686,7 @@ static bool proc_sys_fill_cache(struct f
 		if (d_in_lookup(child)) {
 			struct dentry *res;
 			inode = proc_sys_make_inode(dir->d_sb, head, table);
-			if (!inode) {
+			if (IS_ERR(inode)) {
 				d_lookup_done(child);
 				dput(child);
 				return false;
_

Patches currently in -mm which might be from colona@arista.com are

proc-sysctl-dont-return-enomem-on-lookup-when-a-table-is-unregistering.patch

Re: + proc-sysctl-dont-return-enomem-on-lookup-when-a-table-is-unregistering.patch added to -mm tree

[Luis Chamberlain]

Just a heads up - Al applied a v2 with a modification he made, so
probably best to drop this patch from -mm.

  Luis