linux-kernel - Re: [PATCH] 9p: Avoid creating multiple slab caches with the same name

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Message-ID: <CAHk-=wjpxeTifM1LFPQFR5_RjD2uvDAHbZ-ATCqox+RuFwkbDQ@mail.gmail.com>
Date: Mon, 21 Oct 2024 11:57:38 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Omar Sandoval <osandov@...ndov.com>
Cc: Vlastimil Babka <vbabka@...e.cz>, Dominique Martinet <asmadeus@...ewreck.org>, 
	Thorsten Leemhuis <regressions@...mhuis.info>, Eric Van Hensbergen <ericvh@...nel.org>, 
	Christian Schoenebeck <linux_oss@...debyte.com>, v9fs@...ts.linux.dev, 
	linux-kernel@...r.kernel.org, regressions@...ts.linux.dev, 
	Jason Gunthorpe <jgg@...dia.com>, Pedro Falcato <pedro.falcato@...il.com>
Subject: Re: [PATCH] 9p: Avoid creating multiple slab caches with the same name

On Mon, 21 Oct 2024 at 11:37, Omar Sandoval <osandov@...ndov.com> wrote:
>
> FYI, drgn's CI started getting EIO errors from
> getdents("/sys/kernel/slab") that I bisected to this patch. The problem
> is that dev_name can be an arbitrary string. In my case, it is
> "/dev/root". This trips verify_dirent_name(), which fails if a filename
> contains a slash.

Bah. Does something silly like this fix it:

  --- a/net/9p/client.c
  +++ b/net/9p/client.c
  @@ -977,6 +977,7 @@ static int p9_client_version(struct p9_client *c)
   struct p9_client *p9_client_create(const char *dev_name, char *options)
   {
        int err;
  +     static atomic_t seqno = ATOMIC_INIT(0);
        struct p9_client *clnt;
        char *client_id;
        char *cache_name;
  @@ -1036,7 +1037,8 @@ struct p9_client *p9_client_create(const char
*dev_name, char *options)
        if (err)
                goto close_trans;

  -     cache_name = kasprintf(GFP_KERNEL, "9p-fcall-cache-%s", dev_name);
  +     cache_name = kasprintf(GFP_KERNEL,
  +             "9p-fcall-cache-%d", atomic_inc_return(&seqno));
        if (!cache_name) {
                err = -ENOMEM;
                goto close_trans;

(whitespace-damaged, but you get the idea)

                  Linus