From: Steve French <smfrench@gmail.com>
To: Eric Biggers <ebiggers@kernel.org>
Cc: CIFS <linux-cifs@vger.kernel.org>,
linux-ext4 <linux-ext4@vger.kernel.org>,
syzkaller-bugs@googlegroups.com,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] cifs: clear PF_MEMALLOC before exiting demultiplex thread
Date: Sun, 8 Mar 2020 13:43:56 -0500 [thread overview]
Message-ID: <CAH2r5mtRvs1NkWyvMvO1Pg2OPa9xq=gMUvHLgbA73bsj44DxVQ@mail.gmail.com> (raw)
In-Reply-To: <20200308061611.1185481-1-ebiggers@kernel.org>
merged into cifs-2.6.git for-next
running buildbot cifs/smb3 automated regression tests now
On Sun, Mar 8, 2020 at 12:17 AM Eric Biggers <ebiggers@kernel.org> wrote:
>
> From: Eric Biggers <ebiggers@google.com>
>
> Leaving PF_MEMALLOC set when exiting a kthread causes it to remain set
> during do_exit(). That can confuse things. For example, if BSD process
> accounting is enabled, then it's possible for do_exit() to end up
> calling ext4_write_inode(). That triggers the
> WARN_ON_ONCE(current->flags & PF_MEMALLOC) there, as it assumes
> (appropriately) that inodes aren't written when allocating memory.
>
> This case was reported by syzbot at
> https://lkml.kernel.org/r/0000000000000e7156059f751d7b@google.com.
>
> Fix this in cifs_demultiplex_thread() by using the helper functions to
> save and restore PF_MEMALLOC.
>
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
>
> v2: added missing include of <linux/sched/mm.h>
> (I missed that I didn't actually have CONFIG_CIFS set...)
>
> fs/cifs/connect.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
> index 4804d1df8c1c..97b8eb585cf9 100644
> --- a/fs/cifs/connect.c
> +++ b/fs/cifs/connect.c
> @@ -21,6 +21,7 @@
> #include <linux/fs.h>
> #include <linux/net.h>
> #include <linux/string.h>
> +#include <linux/sched/mm.h>
> #include <linux/sched/signal.h>
> #include <linux/list.h>
> #include <linux/wait.h>
> @@ -1164,8 +1165,9 @@ cifs_demultiplex_thread(void *p)
> struct task_struct *task_to_wake = NULL;
> struct mid_q_entry *mids[MAX_COMPOUND];
> char *bufs[MAX_COMPOUND];
> + unsigned int noreclaim_flag;
>
> - current->flags |= PF_MEMALLOC;
> + noreclaim_flag = memalloc_noreclaim_save();
> cifs_dbg(FYI, "Demultiplex PID: %d\n", task_pid_nr(current));
>
> length = atomic_inc_return(&tcpSesAllocCount);
> @@ -1320,6 +1322,7 @@ cifs_demultiplex_thread(void *p)
> set_current_state(TASK_RUNNING);
> }
>
> + memalloc_noreclaim_restore(noreclaim_flag);
> module_put_and_exit(0);
> }
>
> --
> 2.25.1
>
--
Thanks,
Steve
next prev parent reply other threads:[~2020-03-08 18:44 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-26 6:57 WARNING in ext4_write_inode syzbot
2020-03-08 4:35 ` [PATCH] xfs: clear PF_MEMALLOC before exiting xfsaild thread Eric Biggers
2020-03-08 23:03 ` Dave Chinner
2020-03-09 1:04 ` Eric Biggers
2020-03-09 4:34 ` [PATCH v2] " Eric Biggers
2020-03-09 10:57 ` Brian Foster
2020-03-09 16:24 ` Darrick J. Wong
2020-03-09 18:04 ` Eric Biggers
2020-03-09 18:13 ` Darrick J. Wong
2020-03-09 18:57 ` [PATCH v3] " Eric Biggers
2020-03-10 15:47 ` Darrick J. Wong
2020-03-11 6:34 ` Christoph Hellwig
2020-03-12 22:20 ` [PATCH v2] " Eric Biggers
2020-03-08 4:36 ` [PATCH] cifs: clear PF_MEMALLOC before exiting demultiplex thread Eric Biggers
2020-03-08 6:16 ` [PATCH v2] " Eric Biggers
2020-03-08 18:43 ` Steve French [this message]
2020-03-09 5:56 ` Eric Biggers
2020-03-09 5:58 ` [PATCH v3] " Eric Biggers
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