Re: [PATCH bpf 1/2] bpf: fix alignment of netns_dev/netns_ino fields in bpf_{map,prog}_info

Hi,

Looks like the ABI bug in bpf_map_info and bpf_prog info introduced
in 4.16 is going to slip into 4.17, causing extra pain to 32-bit
userspace.  I'm adding Linus to this thread in hope it might help
to get a fix applied before 4.17 is released.

On Wed, May 30, 2018 at 09:18:58PM +0300, Dmitry V. Levin wrote:

On Sun, May 27, 2018 at 01:28:42PM +0200, Eugene Syromiatnikov wrote:

quoted

Recent introduction of netns_dev/netns_ino to bpf_map_info/bpf_prog info
has broken compat, as offsets of these fields are different in 32-bit
and 64-bit ABIs.  One fix (other than implementing compat support in
syscall in order to handle this discrepancy) is to use __aligned_u64
instead of __u64 for these fields.

Reported-by: Dmitry V. Levin <redacted>
Fixes: 52775b33bb507 ("bpf: offload: report device information about
offloaded maps")
Fixes: 675fc275a3a2d ("bpf: offload: report device information for
offloaded programs")

Signed-off-by: Eugene Syromiatnikov <redacted>

Reviewed-by: "Dmitry V. Levin" <redacted>
Cc: <redacted> # v4.16+

Thanks,

quoted

---
 include/uapi/linux/bpf.h       | 8 ++++----
 tools/include/uapi/linux/bpf.h | 8 ++++----
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index c5ec897..903010a 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h

@@ -1017,8 +1017,8 @@ struct bpf_prog_info {
 	__aligned_u64 map_ids;
 	char name[BPF_OBJ_NAME_LEN];
 	__u32 ifindex;
-	__u64 netns_dev;
-	__u64 netns_ino;
+	__aligned_u64 netns_dev;
+	__aligned_u64 netns_ino;
 } __attribute__((aligned(8)));
 
 struct bpf_map_info {

@@ -1030,8 +1030,8 @@ struct bpf_map_info {
 	__u32 map_flags;
 	char  name[BPF_OBJ_NAME_LEN];
 	__u32 ifindex;
-	__u64 netns_dev;
-	__u64 netns_ino;
+	__aligned_u64 netns_dev;
+	__aligned_u64 netns_ino;
 } __attribute__((aligned(8)));
 
 /* User bpf_sock_addr struct to access socket fields and sockaddr struct passed

diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index c5ec897..903010a 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h

@@ -1017,8 +1017,8 @@ struct bpf_prog_info {
 	__aligned_u64 map_ids;
 	char name[BPF_OBJ_NAME_LEN];
 	__u32 ifindex;
-	__u64 netns_dev;
-	__u64 netns_ino;
+	__aligned_u64 netns_dev;
+	__aligned_u64 netns_ino;
 } __attribute__((aligned(8)));
 
 struct bpf_map_info {

@@ -1030,8 +1030,8 @@ struct bpf_map_info {
 	__u32 map_flags;
 	char  name[BPF_OBJ_NAME_LEN];
 	__u32 ifindex;
-	__u64 netns_dev;
-	__u64 netns_ino;
+	__aligned_u64 netns_dev;
+	__aligned_u64 netns_ino;
 } __attribute__((aligned(8)));
 
 /* User bpf_sock_addr struct to access socket fields and sockaddr struct passed

-- 
ldv