From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37886) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1brPTs-0006kr-Ph for qemu-devel@nongnu.org; Tue, 04 Oct 2016 09:10:05 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1brPTn-0001l0-3a for qemu-devel@nongnu.org; Tue, 04 Oct 2016 09:09:59 -0400 Received: from mail-vk0-x234.google.com ([2607:f8b0:400c:c05::234]:33047) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1brPTm-0001kF-VD for qemu-devel@nongnu.org; Tue, 04 Oct 2016 09:09:55 -0400 Received: by mail-vk0-x234.google.com with SMTP id z126so189267764vkd.0 for ; Tue, 04 Oct 2016 06:09:54 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <1468852560-9054-3-git-send-email-peter.maydell@linaro.org> References: <1468852560-9054-1-git-send-email-peter.maydell@linaro.org> <1468852560-9054-3-git-send-email-peter.maydell@linaro.org> From: Peter Maydell Date: Tue, 4 Oct 2016 14:09:33 +0100 Message-ID: Content-Type: text/plain; charset=UTF-8 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: QEMU Developers Cc: Riku Voipio , Patch Tracking 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? thanks -- PMM 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