From 36f9814a494a874d5a0f44843544b4b2539022db Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Sat, 2 Jun 2018 05:21:59 +0200 Subject: [PATCH] bpf: fix uapi hole for 32 bit compat applications In 64 bit, we have a 4 byte hole between ifindex and netns_dev in the case of struct bpf_map_info but also struct bpf_prog_info. In net-next commit b85fab0e67b ("bpf: Add gpl_compatible flag to struct bpf_prog_info") added a bitfield into it to expose some flags related to programs. Thus, add an unnamed __u32 bitfield for both so that alignment keeps the same in both 32 and 64 bit cases, and can be naturally extended from there as in b85fab0e67b. Before: # file test.o test.o: ELF 32-bit LSB relocatable, Intel 80386, version 1 (SYSV), not stripped # pahole test.o struct bpf_map_info { __u32 type; /* 0 4 */ __u32 id; /* 4 4 */ __u32 key_size; /* 8 4 */ __u32 value_size; /* 12 4 */ __u32 max_entries; /* 16 4 */ __u32 map_flags; /* 20 4 */ char name[16]; /* 24 16 */ __u32 ifindex; /* 40 4 */ __u64 netns_dev; /* 44 8 */ __u64 netns_ino; /* 52 8 */ /* size: 64, cachelines: 1, members: 10 */ /* padding: 4 */ }; After (same as on 64 bit): # file test.o test.o: ELF 32-bit LSB relocatable, Intel 80386, version 1 (SYSV), not stripped # pahole test.o struct bpf_map_info { __u32 type; /* 0 4 */ __u32 id; /* 4 4 */ __u32 key_size; /* 8 4 */ __u32 value_size; /* 12 4 */ __u32 max_entries; /* 16 4 */ __u32 map_flags; /* 20 4 */ char name[16]; /* 24 16 */ __u32 ifindex; /* 40 4 */ /* XXX 4 bytes hole, try to pack */ __u64 netns_dev; /* 48 8 */ __u64 netns_ino; /* 56 8 */ /* --- cacheline 1 boundary (64 bytes) --- */ /* size: 64, cachelines: 1, members: 10 */ /* sum members: 60, holes: 1, sum holes: 4 */ }; Reported-by: Dmitry V. Levin Reported-by: Eugene Syromiatnikov Fixes: 52775b33bb507 ("bpf: offload: report device information about offloaded maps") Fixes: 675fc275a3a2d ("bpf: offload: report device information for offloaded programs") Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: Alexei Starovoitov --- include/uapi/linux/bpf.h | 2 ++ tools/include/uapi/linux/bpf.h | 2 ++ 2 files changed, 4 insertions(+) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index c5ec89732a8d..8c317737ba3f 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -1017,6 +1017,7 @@ struct bpf_prog_info { __aligned_u64 map_ids; char name[BPF_OBJ_NAME_LEN]; __u32 ifindex; + __u32 :32; __u64 netns_dev; __u64 netns_ino; } __attribute__((aligned(8))); @@ -1030,6 +1031,7 @@ struct bpf_map_info { __u32 map_flags; char name[BPF_OBJ_NAME_LEN]; __u32 ifindex; + __u32 :32; __u64 netns_dev; __u64 netns_ino; } __attribute__((aligned(8))); diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index c5ec89732a8d..8c317737ba3f 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -1017,6 +1017,7 @@ struct bpf_prog_info { __aligned_u64 map_ids; char name[BPF_OBJ_NAME_LEN]; __u32 ifindex; + __u32 :32; __u64 netns_dev; __u64 netns_ino; } __attribute__((aligned(8))); @@ -1030,6 +1031,7 @@ struct bpf_map_info { __u32 map_flags; char name[BPF_OBJ_NAME_LEN]; __u32 ifindex; + __u32 :32; __u64 netns_dev; __u64 netns_ino; } __attribute__((aligned(8)));