| Message ID | 20200308061611.1185481-1-ebiggers@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] cifs: clear PF_MEMALLOC before exiting demultiplex thread | expand |
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 >
On Sun, Mar 08, 2020 at 01:43:56PM -0500, Steve French wrote: > merged into cifs-2.6.git for-next > > running buildbot cifs/smb3 automated regression tests now > Thanks. FYI, I also sent a similar patch for an XFS kernel thread, and the XFS folks requested more details in the commit message [1]. So I ended up trying to reproduce this warning on both XFS and CIFS, and I added more details to both commit messages. So if it's not too late, please update the CIFS commit to the v3 I'm sending out. Thanks! [1] https://lkml.kernel.org/linux-xfs/20200308230307.GM10776@dread.disaster.area - Eric
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); }