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@xxxxxxxxxx> wrote: > > From: Eric Biggers <ebiggers@xxxxxxxxxx> > > 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@xxxxxxxxxx. > > Fix this in cifs_demultiplex_thread() by using the helper functions to > save and restore PF_MEMALLOC. > > Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx> > --- > > 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
