| Message ID | 20210928194509.4133465-1-ramjiyani@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [RESEND] aio: Add support for the POLLFREE | expand |
Hi, Ramji, Thanks for the explanation of the use after free. I went ahead and ran the patch through the libaio test suite and it passed. > -#define POLLFREE (__force __poll_t)0x4000 /* currently only for epoll */ > +#define POLLFREE ((__force __poll_t)0x4000) You added parenthesis, here, and I'm not sure if that's a necessary part of this patch. Other than that: Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Hi Jeff: On Tue, Oct 5, 2021 at 12:33 PM Jeff Moyer <jmoyer@redhat.com> wrote: > > Hi, Ramji, > > Thanks for the explanation of the use after free. I went ahead and > ran the patch through the libaio test suite and it passed. > Thanks for taking time to test and providing feedback. > > -#define POLLFREE (__force __poll_t)0x4000 /* currently only for epoll */ > > +#define POLLFREE ((__force __poll_t)0x4000) > > You added parenthesis, here, and I'm not sure if that's a necessary part > of this patch. I added parenthesis to silence the checkpatch script. Should I just ignore it? I'll send v2 with the change, if it is required. > > Other than that: > > Reviewed-by: Jeff Moyer <jmoyer@redhat.com> > Thanks, Ramji
Hi, Ramji, Ramji Jiyani <ramjiyani@google.com> writes: > Hi Jeff: > > On Tue, Oct 5, 2021 at 12:33 PM Jeff Moyer <jmoyer@redhat.com> wrote: >> >> Hi, Ramji, >> >> Thanks for the explanation of the use after free. I went ahead and >> ran the patch through the libaio test suite and it passed. >> > > Thanks for taking time to test and providing feedback. > >> > -#define POLLFREE (__force __poll_t)0x4000 /* currently only for epoll */ >> > +#define POLLFREE ((__force __poll_t)0x4000) >> >> You added parenthesis, here, and I'm not sure if that's a necessary part >> of this patch. > > I added parenthesis to silence the checkpatch script. Should I just ignore it? > I'll send v2 with the change, if it is required. None of the other #defines in that file use parens, so it would, at the very least, be inconsistent. I would leave the the parens out. Cheers, Jeff
diff --git a/fs/aio.c b/fs/aio.c index 51b08ab01dff..5d539c05df42 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -1674,6 +1674,7 @@ static int aio_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync, { struct poll_iocb *req = container_of(wait, struct poll_iocb, wait); struct aio_kiocb *iocb = container_of(req, struct aio_kiocb, poll); + struct kioctx *ctx = iocb->ki_ctx; __poll_t mask = key_to_poll(key); unsigned long flags; @@ -1683,29 +1684,33 @@ static int aio_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync, list_del_init(&req->wait.entry); - if (mask && spin_trylock_irqsave(&iocb->ki_ctx->ctx_lock, flags)) { - struct kioctx *ctx = iocb->ki_ctx; + /* + * Use irqsave/irqrestore because not all filesystems (e.g. fuse) + * call this function with IRQs disabled and because IRQs have to + * be disabled before ctx_lock is obtained. + */ + if (mask & POLLFREE) { + /* Force complete iocb inline to remove refs to deleted entry */ + spin_lock_irqsave(&ctx->ctx_lock, flags); + } else if (!(mask && spin_trylock_irqsave(&ctx->ctx_lock, flags))) { + /* Can't complete iocb inline; schedule for later */ + schedule_work(&req->work); + return 1; + } - /* - * Try to complete the iocb inline if we can. Use - * irqsave/irqrestore because not all filesystems (e.g. fuse) - * call this function with IRQs disabled and because IRQs - * have to be disabled before ctx_lock is obtained. - */ - list_del(&iocb->ki_list); - iocb->ki_res.res = mangle_poll(mask); - req->done = true; - if (iocb->ki_eventfd && eventfd_signal_allowed()) { - iocb = NULL; - INIT_WORK(&req->work, aio_poll_put_work); - schedule_work(&req->work); - } - spin_unlock_irqrestore(&ctx->ctx_lock, flags); - if (iocb) - iocb_put(iocb); - } else { + /* complete iocb inline */ + list_del(&iocb->ki_list); + iocb->ki_res.res = mangle_poll(mask); + req->done = true; + if (iocb->ki_eventfd && eventfd_signal_allowed()) { + iocb = NULL; + INIT_WORK(&req->work, aio_poll_put_work); schedule_work(&req->work); } + spin_unlock_irqrestore(&ctx->ctx_lock, flags); + if (iocb) + iocb_put(iocb); + return 1; } diff --git a/include/uapi/asm-generic/poll.h b/include/uapi/asm-generic/poll.h index 41b509f410bf..35b1b69af729 100644 --- a/include/uapi/asm-generic/poll.h +++ b/include/uapi/asm-generic/poll.h @@ -29,7 +29,7 @@ #define POLLRDHUP 0x2000 #endif -#define POLLFREE (__force __poll_t)0x4000 /* currently only for epoll */ +#define POLLFREE ((__force __poll_t)0x4000) #define POLL_BUSY_LOOP (__force __poll_t)0x8000
Commit f5cb779ba163 ("ANDROID: binder: remove waitqueue when thread exits.") fixed the use-after-free in eventpoll but aio still has the same issue because it doesn't honor the POLLFREE flag. Add support for the POLLFREE flag to force complete iocb inline in aio_poll_wake(). A thread may use it to signal it's exit and/or request to cleanup while pending poll request. In this case, aio_poll_wake() needs to make sure it doesn't keep any reference to the queue entry before returning from wake to avoid possible use after free via poll_cancel() path. The POLLFREE flag is no more exclusive to the epoll and is being shared with the aio. Remove comment from poll.h to avoid confusion. Also enclosed the POLLFREE macro definition in parentheses to fix checkpatch error. Signed-off-by: Ramji Jiyani <ramjiyani@google.com> --- fs/aio.c | 45 ++++++++++++++++++--------------- include/uapi/asm-generic/poll.h | 2 +- 2 files changed, 26 insertions(+), 21 deletions(-)