Hi Roland, Le jeudi 22 mai 2014 à 08:21 +0200, Yann Droneaud a écrit : > Le lundi 05 mai 2014 à 19:35 +0200, Yann Droneaud a écrit : > > i386 ABI disagree with most other ABIs regarding alignment > > of data type larger than 4 bytes: on most ABIs a padding must > > be added at end of the structures, while it is not required on > > i386. > > > > So for most ABI struct c4iw_alloc_ucontext_resp get implicitly padded > > to be aligned on a 8 bytes multiple, while for i386, such padding > > is not added. > > > > Tool pahole could be used to find such implicit padding: > > > > $ pahole --anon_include \ > > --nested_anon_include \ > > --recursive \ > > --class_name c4iw_alloc_ucontext_resp \ > > drivers/infiniband/hw/cxgb4/iw_cxgb4.o > > > > Then, structure layout can be compared between i386 and x86_64: > > > > +++ obj-i386/drivers/infiniband/hw/cxgb4/iw_cxgb4.o.pahole.txt > > 2014-03-28 11:43:05.547432195 +0100 > > --- obj-x86_64/drivers/infiniband/hw/cxgb4/iw_cxgb4.o.pahole.txt > > 2014-03-28 10:55:10.990133017 +0100 > > @@ -2,9 +2,8 @@ struct c4iw_alloc_ucontext_resp { > > __u64 status_page_key; /* 0 8 */ > > __u32 status_page_size; /* 8 4 */ > > > > - /* size: 12, cachelines: 1, members: 2 */ > > - /* last cacheline: 12 bytes */ > > + /* size: 16, cachelines: 1, members: 2 */ > > + /* padding: 4 */ > > + /* last cacheline: 16 bytes */ > > }; > > > > This ABI disagreement will make an x86_64 kernel try to write > > past the buffer provided by an i386 binary. > > > > When boundary check will be implemented, the x86_64 kernel will > > refuse to write past the i386 userspace provided buffer > > and the uverbs will fail. > > > > If the structure lay in memory on a page boundary and next page > > is not mapped, ib_copy_to_udata() will fail and the uverb > > will fail. > > > > Additionally, as reported by Dan Carpenter, without the implicit > > padding being properly cleared, an information leak would take > > place in most architectures. > > > > This patch adds an explicit padding to struct c4iw_alloc_ucontext_resp, > > and, like 92b0ca7cb149 ('IB/mlx5: Fix stack info leak in > > mlx5_ib_alloc_ucontext()'), makes function c4iw_alloc_ucontext() > > not writting this padding field to userspace. This way, x86_64 kernel > > will be able to write struct c4iw_alloc_ucontext_resp as expected by > > unpatched and patched i386 libcxgb4. > > > > Link: http://marc.info/?i=cover.1399309513.git.ydrone...@opteya.com > > Link: http://marc.info/?i=1395848977.3297.15.camel@localhost.localdomain > > Link: http://marc.info/?i=20140328082428.GH25192@mwanda > > Fixes: 05eb23893c2c ('cxgb4/iw_cxgb4: Doorbell Drop Avoidance Bug Fixes') > > Reported-by: Yann Droneaud <ydrone...@opteya.com> > > Reported-by: Dan Carpenter <dan.carpen...@oracle.com> > > Signed-off-by: Yann Droneaud <ydrone...@opteya.com> > > I believe this one should go in v3.15-rc7 as it fixes an issue > introduced in v3.15-rc1. See > http://marc.info/?i=20140328082428.GH25192@mwanda > http://marc.info/?i=20140502235616.GJ4963@mwanda > > The other patchs could probably wait for v3.16-rc1 for integration in > linux-stable. >
I think this patch is likely not going to v3.15, so in order to have it integrated in v3.15.x with the others, could you add Cc: <sta...@vger.kernel.org> to this patch the next time you rebuild your 'for-next' branch ? Cc: <sta...@vger.kernel.org> Thanks a lot. Regards. -- Yann Droneaud OPTEYA -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html