search for: set_bit_to_user

Vhost log dirty pages directly to a userspace bitmap through GUP and kmap_atomic() since kernel doesn't have a set_bit_to_user() helper. This will cause issues for the arch that has virtually tagged caches. The way to fix is to keep using userspace virtual address. Fortunately, futex has arch_futex_atomic_op_inuser() which could be used for setting a bit to user. Note: - There're archs (few non popular ones) that don&...

Vhost log dirty pages directly to a userspace bitmap through GUP and kmap_atomic() since kernel doesn't have a set_bit_to_user() helper. This will cause issues for the arch that has virtually tagged caches. The way to fix is to keep using userspace virtual address. Fortunately, futex has arch_futex_atomic_op_inuser() which could be used for setting a bit to user. Note: - There're archs (few non popular ones) that don&...

Vhost log dirty pages directly to a userspace bitmap through GUP and kmap_atomic() since kernel doesn't have a set_bit_to_user() helper. This will cause issues for the arch that has virtually tagged caches. The way to fix is to keep using userspace virtual address. Fortunately, futex has a cmpxchg to userspace memory helper futex_atomic_cmpxchg_inatomic(). So switch to use it to exchange the userspace bitmap with zero, se...

Vhost log dirty pages directly to a userspace bitmap through GUP and kmap_atomic() since kernel doesn't have a set_bit_to_user() helper. This will cause issues for the arch that has virtually tagged caches. The way to fix is to keep using userspace virtual address. Fortunately, futex has a cmpxchg to userspace memory helper futex_atomic_cmpxchg_inatomic(). So switch to use it to exchange the userspace bitmap with zero, se...

Vhost log dirty pages directly to a userspace bitmap through GUP and kmap_atomic() since kernel doesn't have a set_bit_to_user() helper. This will cause issues for the arch that has virtually tagged caches. The way to fix is to keep using userspace virtual address. Fortunately, futex has arch_futex_atomic_op_inuser() which could be used for setting a bit to user. Note there're several cases that futex helper can fail...

Vhost log dirty pages directly to a userspace bitmap through GUP and kmap_atomic() since kernel doesn't have a set_bit_to_user() helper. This will cause issues for the arch that has virtually tagged caches. The way to fix is to keep using userspace virtual address. Fortunately, futex has arch_futex_atomic_op_inuser() which could be used for setting a bit to user. Note there're several cases that futex helper can fail...

From: "Michael S. Tsirkin" <mst at redhat.com> Date: Mon, 11 Mar 2019 09:59:28 -0400 > On Mon, Mar 11, 2019 at 03:13:17PM +0800, Jason Wang wrote: >> >> On 2019/3/8 ??10:12, Christoph Hellwig wrote: >> > On Wed, Mar 06, 2019 at 02:18:07AM -0500, Jason Wang wrote: >> > > This series tries to access virtqueue metadata through kernel virtual

From: "Michael S. Tsirkin" <mst at redhat.com> Date: Mon, 11 Mar 2019 09:59:28 -0400 > On Mon, Mar 11, 2019 at 03:13:17PM +0800, Jason Wang wrote: >> >> On 2019/3/8 ??10:12, Christoph Hellwig wrote: >> > On Wed, Mar 06, 2019 at 02:18:07AM -0500, Jason Wang wrote: >> > > This series tries to access virtqueue metadata through kernel virtual

On Mon, May 13, 2019 at 01:27:45AM -0400, Jason Wang wrote: > Vhost log dirty pages directly to a userspace bitmap through GUP and > kmap_atomic() since kernel doesn't have a set_bit_to_user() > helper. This will cause issues for the arch that has virtually tagged > caches. The way to fix is to keep using userspace virtual > address. Fortunately, futex has arch_futex_atomic_op_inuser() which > could be used for setting a bit to user. > > Note there're several cas...

On Thu, May 09, 2019 at 08:58:00AM -0400, Jason Wang wrote: > Vhost log dirty pages directly to a userspace bitmap through GUP and > kmap_atomic() since kernel doesn't have a set_bit_to_user() > helper. This will cause issues for the arch that has virtually tagged > caches. The way to fix is to keep using userspace virtual > address. Fortunately, futex has arch_futex_atomic_op_inuser() which > could be used for setting a bit to user. > > Note: > - There're arc...

On Mon, May 06, 2019 at 10:23:29PM -0400, Jason Wang wrote: > Vhost log dirty pages directly to a userspace bitmap through GUP and > kmap_atomic() since kernel doesn't have a set_bit_to_user() > helper. This will cause issues for the arch that has virtually tagged > caches. The way to fix is to keep using userspace virtual address. > > Fortunately, futex has a cmpxchg to userspace memory helper > futex_atomic_cmpxchg_inatomic(). So switch to use it to exchange the >...

On 2019/5/9 ??9:18, Michael S. Tsirkin wrote: > On Thu, May 09, 2019 at 08:58:00AM -0400, Jason Wang wrote: >> Vhost log dirty pages directly to a userspace bitmap through GUP and >> kmap_atomic() since kernel doesn't have a set_bit_to_user() >> helper. This will cause issues for the arch that has virtually tagged >> caches. The way to fix is to keep using userspace virtual >> address. Fortunately, futex has arch_futex_atomic_op_inuser() which >> could be used for setting a bit to user. >> >> Note:...

On 2019/5/9 ??9:18, Michael S. Tsirkin wrote: > On Thu, May 09, 2019 at 08:58:00AM -0400, Jason Wang wrote: >> Vhost log dirty pages directly to a userspace bitmap through GUP and >> kmap_atomic() since kernel doesn't have a set_bit_to_user() >> helper. This will cause issues for the arch that has virtually tagged >> caches. The way to fix is to keep using userspace virtual >> address. Fortunately, futex has arch_futex_atomic_op_inuser() which >> could be used for setting a bit to user. >> >> Note:...

Vq log_base is the userspace address of bitmap which has nothing to do with IOTLB. So it needs to be validated unconditionally otherwise we may try use 0 as log_base which may lead to pin pages that will lead unexpected result (e.g trigger BUG_ON() in set_bit_to_user()). Fixes: 6b1e6cc7855b0 ("vhost: new device IOTLB API") Reported-by: syzbot+6304bf97ef436580fede at syzkaller.appspotmail.com Signed-off-by: Jason Wang <jasowang at redhat.com> --- drivers/vhost/vhost.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) diff --...

Vq log_base is the userspace address of bitmap which has nothing to do with IOTLB. So it needs to be validated unconditionally otherwise we may try use 0 as log_base which may lead to pin pages that will lead unexpected result (e.g trigger BUG_ON() in set_bit_to_user()). Fixes: 6b1e6cc7855b0 ("vhost: new device IOTLB API") Reported-by: syzbot+6304bf97ef436580fede at syzkaller.appspotmail.com Signed-off-by: Jason Wang <jasowang at redhat.com> --- drivers/vhost/vhost.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) diff --...

...by: Jason Wang <jasowang at redhat.com> --- drivers/vhost/vhost.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 351af88231ad..34a1cedbc5ba 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -1711,6 +1711,7 @@ static int set_bit_to_user(int nr, void __user *addr) base = kmap_atomic(page); set_bit(bit, base); kunmap_atomic(base); + flush_dcache_page(page); set_page_dirty_lock(page); put_page(page); return 0; -- 2.19.1

...by: Jason Wang <jasowang at redhat.com> --- drivers/vhost/vhost.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 351af88231ad..34a1cedbc5ba 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -1711,6 +1711,7 @@ static int set_bit_to_user(int nr, void __user *addr) base = kmap_atomic(page); set_bit(bit, base); kunmap_atomic(base); + flush_dcache_page(page); set_page_dirty_lock(page); put_page(page); return 0; -- 2.19.1

...nel and userspace view of memory >> might not be automatically in sync if they access memory >> through different virtual addresses. You need to do things like >> flush_cache_page, probably multiple times. > "flush_dcache_page()" I get this. Then I think the current set_bit_to_user() is suspicious, we probably miss a flush_dcache_page() there: static int set_bit_to_user(int nr, void __user *addr) { ??????? unsigned long log = (unsigned long)addr; ??????? struct page *page; ??????? void *base; ??????? int bit = nr + (log % PAGE_SIZE) * 8; ??????? int r; ??????? r = g...

...; might not be automatically in sync if they access memory >>>> through different virtual addresses. You need to do things like >>>> flush_cache_page, probably multiple times. >>> "flush_dcache_page()" >> >> I get this. Then I think the current set_bit_to_user() is suspicious, >> we >> probably miss a flush_dcache_page() there: >> >> >> static int set_bit_to_user(int nr, void __user *addr) >> { >> unsigned long log = (unsigned long)addr; >> struct page *page; >> void *bas...

...; might not be automatically in sync if they access memory >>>> through different virtual addresses. You need to do things like >>>> flush_cache_page, probably multiple times. >>> "flush_dcache_page()" >> >> I get this. Then I think the current set_bit_to_user() is suspicious, we >> probably miss a flush_dcache_page() there: >> >> >> static int set_bit_to_user(int nr, void __user *addr) >> { >> ??????? unsigned long log = (unsigned long)addr; >> ??????? struct page *page; >> ??????? void *base; >>...