| Message ID | b7ae23be3a3d4a2f57eca6cfc7f9361da883ceca.1377372576.git.ydroneaud@opteya.com |
|---|---|
| State | New, archived |
| Headers | show |
On 24.08.2013, at 21:14, Yann Droneaud wrote: > KVM uses anon_inode_get() to allocate file descriptors as part > of some of its ioctls. But those ioctls are lacking a flag argument > allowing userspace to choose options for the newly opened file descriptor. > > In such case it's advised to use O_CLOEXEC by default so that > userspace is allowed to choose, without race, if the file descriptor > is going to be inherited across exec(). > > This patch set O_CLOEXEC flag on all file descriptors created > with anon_inode_getfd() to not leak file descriptors across exec(). > > Signed-off-by: Yann Droneaud <ydroneaud@opteya.com> > Link: http://lkml.kernel.org/r/cover.1377372576.git.ydroneaud@opteya.com Reviewed-by: Alexander Graf <agraf@suse.de> Would it make sense to simply inherit the O_CLOEXEC flag from the parent kvm fd instead? That would give user space the power to keep fds across exec() if it wants to. Alex -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Il 25/08/2013 17:04, Alexander Graf ha scritto: > > On 24.08.2013, at 21:14, Yann Droneaud wrote: > >> KVM uses anon_inode_get() to allocate file descriptors as part >> of some of its ioctls. But those ioctls are lacking a flag argument >> allowing userspace to choose options for the newly opened file descriptor. >> >> In such case it's advised to use O_CLOEXEC by default so that >> userspace is allowed to choose, without race, if the file descriptor >> is going to be inherited across exec(). >> >> This patch set O_CLOEXEC flag on all file descriptors created >> with anon_inode_getfd() to not leak file descriptors across exec(). >> >> Signed-off-by: Yann Droneaud <ydroneaud@opteya.com> >> Link: http://lkml.kernel.org/r/cover.1377372576.git.ydroneaud@opteya.com > > Reviewed-by: Alexander Graf <agraf@suse.de> > > Would it make sense to simply inherit the O_CLOEXEC flag from the > parent kvm fd instead? That would give user space the power to keep > fds across exec() if it wants to. Does it make sense to use non-O_CLOEXEC file descriptors with KVM at all? Besides fork() not being supported by KVM, as described in Documentation/virtual/kvm/api.txt, the VMAs of the parent process go away as soon as you exec(). I'm not sure how you can use the inherited file descriptor in a sensible way after exec(). Paolo -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Le 26.08.2013 09:39, Paolo Bonzini a écrit : > Il 25/08/2013 17:04, Alexander Graf ha scritto: >> On 24.08.2013, at 21:14, Yann Droneaud wrote: >> >>> >>> This patch set O_CLOEXEC flag on all file descriptors created >>> with anon_inode_getfd() to not leak file descriptors across exec(). >>> >>> Signed-off-by: Yann Droneaud <ydroneaud@opteya.com> >>> Link: >>> http://lkml.kernel.org/r/cover.1377372576.git.ydroneaud@opteya.com >> >> Reviewed-by: Alexander Graf <agraf@suse.de> >> >> Would it make sense to simply inherit the O_CLOEXEC flag from the >> parent kvm fd instead? That would give user space the power to keep >> fds across exec() if it wants to. > > Does it make sense to use non-O_CLOEXEC file descriptors with KVM at > all? Besides fork() not being supported by KVM, as described in > Documentation/virtual/kvm/api.txt, the VMAs of the parent process go > away as soon as you exec(). I'm not sure how you can use the inherited > file descriptor in a sensible way after exec(). > Sounds a lot like InfiniBand subsystem behavor: IB file descriptors are of no use accross exec() since memory mappings tied to those fds won't be available in the new process: https://lkml.org/lkml/2013/7/8/380 http://mid.gmane.org/f58540dc64fec1ac0e496dfcd3cc1af7@meuh.org Regards.
Il 26/08/2013 10:23, Yann Droneaud ha scritto: > > Sounds a lot like InfiniBand subsystem behavor: IB file descriptors > are of no use accross exec() since memory mappings tied to those fds > won't be available in the new process: > > https://lkml.org/lkml/2013/7/8/380 > http://mid.gmane.org/f58540dc64fec1ac0e496dfcd3cc1af7@meuh.org Yes, it is very similar. Paolo -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c index 710d313..f7c9e8a 100644 --- a/arch/powerpc/kvm/book3s_64_mmu_hv.c +++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c @@ -1579,7 +1579,7 @@ int kvm_vm_ioctl_get_htab_fd(struct kvm *kvm, struct kvm_get_htab_fd *ghf) ctx->first_pass = 1; rwflag = (ghf->flags & KVM_GET_HTAB_WRITE) ? O_WRONLY : O_RDONLY; - ret = anon_inode_getfd("kvm-htab", &kvm_htab_fops, ctx, rwflag); + ret = anon_inode_getfd("kvm-htab", &kvm_htab_fops, ctx, rwflag | O_CLOEXEC); if (ret < 0) { kvm_put_kvm(kvm); return ret; diff --git a/arch/powerpc/kvm/book3s_64_vio.c b/arch/powerpc/kvm/book3s_64_vio.c index b2d3f3b..54cf9bc 100644 --- a/arch/powerpc/kvm/book3s_64_vio.c +++ b/arch/powerpc/kvm/book3s_64_vio.c @@ -136,7 +136,7 @@ long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm, mutex_unlock(&kvm->lock); return anon_inode_getfd("kvm-spapr-tce", &kvm_spapr_tce_fops, - stt, O_RDWR); + stt, O_RDWR | O_CLOEXEC); fail: if (stt) { diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index e8d51cb..3503829 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -1556,7 +1556,7 @@ long kvm_vm_ioctl_allocate_rma(struct kvm *kvm, struct kvm_allocate_rma *ret) if (!ri) return -ENOMEM; - fd = anon_inode_getfd("kvm-rma", &kvm_rma_fops, ri, O_RDWR); + fd = anon_inode_getfd("kvm-rma", &kvm_rma_fops, ri, O_RDWR | O_CLOEXEC); if (fd < 0) kvm_release_rma(ri);
KVM uses anon_inode_get() to allocate file descriptors as part of some of its ioctls. But those ioctls are lacking a flag argument allowing userspace to choose options for the newly opened file descriptor. In such case it's advised to use O_CLOEXEC by default so that userspace is allowed to choose, without race, if the file descriptor is going to be inherited across exec(). This patch set O_CLOEXEC flag on all file descriptors created with anon_inode_getfd() to not leak file descriptors across exec(). Signed-off-by: Yann Droneaud <ydroneaud@opteya.com> Link: http://lkml.kernel.org/r/cover.1377372576.git.ydroneaud@opteya.com --- arch/powerpc/kvm/book3s_64_mmu_hv.c | 2 +- arch/powerpc/kvm/book3s_64_vio.c | 2 +- arch/powerpc/kvm/book3s_hv.c | 2 +- 3 files changed, 3 insertions(+), 3 deletions(-)