From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35010) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1brr9j-0008No-NT for qemu-devel@nongnu.org; Wed, 05 Oct 2016 14:43:04 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1brr9e-0001IZ-6p for qemu-devel@nongnu.org; Wed, 05 Oct 2016 14:43:03 -0400 Received: from jessie.kos.to ([212.47.231.226]:34570 helo=pilvi.kos.to) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1brr9d-0001HD-TF for qemu-devel@nongnu.org; Wed, 05 Oct 2016 14:42:58 -0400 Date: Wed, 5 Oct 2016 21:42:50 +0300 From: Riku Voipio Message-ID: <20161005184250.GA22568@beaming.home> References: <1468852560-9054-1-git-send-email-peter.maydell@linaro.org> <1468852560-9054-3-git-send-email-peter.maydell@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] [PATCH 2/2] linux-user: Don't use alloca() for epoll_wait's epoll event array List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Maydell Cc: QEMU Developers , Patch Tracking On Tue, Oct 04, 2016 at 02:09:33PM +0100, Peter Maydell wrote: > Ping? It looks like patch 1/2 of this series got into the > recent linux-user pullreq, but this one (2/2) didn't. Do > you want a resend as a standalone patch? No need, I've pulled it from patchwork, for some reason this didn't get to my mailbox... > On 18 July 2016 at 15:36, Peter Maydell wrote: > > The epoll event array which epoll_wait() allocates has a size > > determined by the guest which could potentially be quite large. > > Use g_try_new() rather than alloca() so that we can fail more > > cleanly if the guest hands us an oversize value. (ENOMEM is > > not a documented return value for epoll_wait() but in practice > > some kernel configurations can return it -- see for instance > > sys_oabi_epoll_wait() on ARM.) > > > > This rearrangement includes fixing a bug where we were > > incorrectly passing a negative length to unlock_user() in > > the error-exit codepath. > > > > Signed-off-by: Peter Maydell > > --- > > linux-user/syscall.c | 17 +++++++++++++---- > > 1 file changed, 13 insertions(+), 4 deletions(-) > > > > diff --git a/linux-user/syscall.c b/linux-user/syscall.c > > index 3552295..721d7b1 100644 > > --- a/linux-user/syscall.c > > +++ b/linux-user/syscall.c > > @@ -11035,7 +11035,12 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, > > goto efault; > > } > > > > - ep = alloca(maxevents * sizeof(struct epoll_event)); > > + ep = g_try_new(struct epoll_event, maxevents); > > + if (!ep) { > > + unlock_user(target_ep, arg2, 0); > > + ret = -TARGET_ENOMEM; > > + break; > > + } > > > > switch (num) { > > #if defined(TARGET_NR_epoll_pwait) > > @@ -11053,8 +11058,8 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, > > target_set = lock_user(VERIFY_READ, arg5, > > sizeof(target_sigset_t), 1); > > if (!target_set) { > > - unlock_user(target_ep, arg2, 0); > > - goto efault; > > + ret = -TARGET_EFAULT; > > + break; > > } > > target_to_host_sigset(set, target_set); > > unlock_user(target_set, arg5, 0); > > @@ -11082,8 +11087,12 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, > > target_ep[i].events = tswap32(ep[i].events); > > target_ep[i].data.u64 = tswap64(ep[i].data.u64); > > } > > + unlock_user(target_ep, arg2, > > + ret * sizeof(struct target_epoll_event)); > > + } else { > > + unlock_user(target_ep, arg2, 0); > > } > > - unlock_user(target_ep, arg2, ret * sizeof(struct target_epoll_event)); > > + g_free(ep); > > break; > > } > > #endif > > -- > > 1.9.1