Subject: Re: "bpf: Improve the info.func_info and info.func_info_rec_size behavior" breaks strace self tests

From: Heiko Carstens <[email-masked]>
Date: Thu, 3 Jan 2019 23:41:18 +0100

On Thu, Jan 03, 2019 at 07:12:05PM +0000, Martin Lau wrote:
> On Thu, Jan 03, 2019 at 12:46:13PM +0100, Heiko Carstens wrote:
> > Hello,
> > 
> > the kernel commit 7337224fc150 ("bpf: Improve the info.func_info and
> > info.func_info_rec_size behavior") breaks one of strace's self tests:
> > 
> > FAIL: bpf-obj_get_info_by_fd-prog-v.gen
> The strace's bpf-obj_get_info_by_fd-prog-v test did fail.  However,
> I failed to see how 7337224fc150 broke it.  How do you trace down to
> commit 7337224fc150 and can you share your test output?
> 
> The failure I can reproduce is EFAULT.  It should have been failing
> as early as "nr_jited_ksyms" is added to "struct bpf_prog_info"
> in linux/bpf.h.

Ah, sorry(!), I forgot to mention an important detail: the test
failure happens only if executed as normal (non-root) user.

With 7337224fc150 ("bpf: Improve the info.func_info and
info.func_info_rec_size behavior") the failure happens. With commit
30da46b5dc3a ("tools: bpftool: add a command to dump the trace pipe")
it passes; which is one commit earlier.

FAIL: bpf-obj_get_info_by_fd-prog-v.gen
=======================================

--- exp	2019-01-03 23:31:49.576949303 +0100
+++ log	2019-01-03 23:31:49.576949303 +0100
@@ -1,8 +1,8 @@
 bpf(BPF_MAP_CREATE, {map_type=BPF_MAP_TYPE_ARRAY, key_size=4, value_size=8, max_entries=1, map_flags=0, inner_map_fd=0</dev/null>, map_name="test_map", map_ifindex=0}, 48) = 3<anon_inode:bpf-map>
 bpf(BPF_PROG_LOAD, {prog_type=BPF_PROG_TYPE_SOCKET_FILTER, insn_cnt=9, insns=[{code=BPF_ALU64|BPF_K|BPF_MOV, dst_reg=BPF_REG_1, src_reg=BPF_REG_0, off=0, imm=0}, {code=BPF_STX|BPF_W|BPF_MEM, dst_reg=BPF_REG_10, src_reg=BPF_REG_1, off=-4, imm=0}, {code=BPF_ALU64|BPF_X|BPF_MOV, dst_reg=BPF_REG_2, src_reg=BPF_REG_10, off=0, imm=0}, {code=BPF_ALU64|BPF_K|BPF_ADD, dst_reg=BPF_REG_2, src_reg=BPF_REG_0, off=0, imm=0xfffffffc}, {code=BPF_LD|BPF_DW|BPF_IMM, dst_reg=BPF_REG_1, src_reg=BPF_REG_1, off=0, imm=0x3}, {code=BPF_LD|BPF_W|BPF_IMM, dst_reg=BPF_REG_0, src_reg=BPF_REG_0, off=0, imm=0}, {code=BPF_JMP|BPF_K|BPF_CALL, dst_reg=BPF_REG_0, src_reg=BPF_REG_0, off=0, imm=0x1}, {code=BPF_ALU64|BPF_K|BPF_MOV, dst_reg=BPF_REG_0, src_reg=BPF_REG_0, off=0, imm=0}, {code=BPF_JMP|BPF_K|BPF_EXIT, dst_reg=BPF
 _REG_0, src_reg=BPF_REG_0, off=0, imm=0}], license="BSD", log_level=42, log_size=4096, log_buf="", kern_version=KERNEL_VERSION(57005, 192, 222), prog_flags=0, prog_name="test_prog", prog_ifindex=0, expected_attach_type=BPF_CGROUP_INET_INGRESS}, 72) = 4<anon_inode:bpf-prog>
 bpf(BPF_OBJ_GET_INFO_BY_FD, {info={bpf_fd=3<anon_inode:bpf-map>, info_len=128 => 80, info={type=BPF_MAP_TYPE_ARRAY, id=15, key_size=4, value_size=8, max_entries=1, map_flags=0, name="test_map", ifindex=0, netns_dev=makedev(0, 0), netns_ino=0}}}, 16) = 0
-bpf(BPF_OBJ_GET_INFO_BY_FD, {info={bpf_fd=4<anon_inode:bpf-prog>, info_len=168 => 152, info={type=BPF_PROG_TYPE_SOCKET_FILTER, id=8, tag="\xde\x90\x83\x18\xfb\x16\xd8\x9c", jited_prog_len=0, jited_prog_insns=NULL, xlated_prog_len=0, xlated_prog_insns=NULL, load_time=28281352029, created_by_uid=1000, nr_map_ids=0 => 1, map_ids=NULL, name="test_prog", ifindex=0, netns_dev=makedev(0, 0), netns_ino=0}}}, 16) = 0
-bpf(BPF_OBJ_GET_INFO_BY_FD, {info={bpf_fd=4<anon_inode:bpf-prog>, info_len=152, info={type=BPF_PROG_TYPE_SOCKET_FILTER, id=8, tag="\xde\x90\x83\x18\xfb\x16\xd8\x9c", jited_prog_len=0, jited_prog_insns=NULL, xlated_prog_len=336, xlated_prog_insns=0x3ff8d6f7000, load_time=28281352029, created_by_uid=1000, nr_map_ids=2, map_ids=0x3ff8d6f1000, name="test_prog", ifindex=0, netns_dev=makedev(0, 0), netns_ino=0}}}, 16) = -1 EFAULT (Bad address)
-bpf(BPF_OBJ_GET_INFO_BY_FD, {info={bpf_fd=4<anon_inode:bpf-prog>, info_len=152, info={type=BPF_PROG_TYPE_SOCKET_FILTER, id=8, tag="\xde\x90\x83\x18\xfb\x16\xd8\x9c", jited_prog_len=0, jited_prog_insns=NULL, xlated_prog_len=0, xlated_prog_insns=[], load_time=28281352029, created_by_uid=1000, nr_map_ids=0 => 1, map_ids=[], name="test_prog", ifindex=0, netns_dev=makedev(0, 0), netns_ino=0}}}, 16) = 0
-bpf(BPF_OBJ_GET_INFO_BY_FD, {info={bpf_fd=4<anon_inode:bpf-prog>, info_len=152, info={type=BPF_PROG_TYPE_SOCKET_FILTER, id=8, tag="\xde\x90\x83\x18\xfb\x16\xd8\x9c", jited_prog_len=0, jited_prog_insns=NULL, xlated_prog_len=0, xlated_prog_insns=[], load_time=28281352029, created_by_uid=1000, nr_map_ids=2 => 1, map_ids=[15], name="test_prog", ifindex=0, netns_dev=makedev(0, 0), netns_ino=0}}}, 16) = 0
+bpf(BPF_OBJ_GET_INFO_BY_FD, {info={bpf_fd=4<anon_inode:bpf-prog>, info_len=168 => 152, info={type=BPF_PROG_TYPE_SOCKET_FILTER, id=8, tag="\xde\x90\x83\x18\xfb\x16\xd8\x9c", jited_prog_len=0, jited_prog_insns=NULL, xlated_prog_len=0, xlated_prog_insns=NULL, load_time=28281352029, created_by_uid=1000, nr_map_ids=0 => 1, map_ids=NULL, name="test_prog", ifindex=0, netns_dev=makedev(0, 0), netns_ino=0, /* bytes 104..151 */ "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"}}}, 16) = 0
+bpf(BPF_OBJ_GET_INFO_BY_FD, {info={bpf_fd=4<anon_inode:bpf-prog>, info_len=152, info={type=BPF_PROG_TYPE_SOCKET_FILTER, id=8, tag="\xde\x90\x83\x18\xfb\x16\xd8\x9c", jited_prog_len=0, jited_prog_insns=NULL, xlated_prog_len=336, xlated_prog_insns=0x3ff8d6f7000, load_time=28281352029, created_by_uid=1000, nr_map_ids=2, map_ids=0x3ff8d6f1000, name="test_prog", ifindex=0, netns_dev=makedev(0, 0), netns_ino=0, /* bytes 104..151 */ "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"}}}, 16) = -1 EFAULT (Bad address)
+bpf(BPF_OBJ_GET_INFO_BY_FD, {info={bpf_fd=4<anon_inode:bpf-prog>, info_len=152, info={type=BPF_PROG_TYPE_SOCKET_FILTER, id=8, tag="\xde\x90\x83\x18\xfb\x16\xd8\x9c", jited_prog_len=0, jited_prog_insns=NULL, xlated_prog_len=0, xlated_prog_insns=[], load_time=28281352029, created_by_uid=1000, nr_map_ids=0 => 1, map_ids=[], name="test_prog", ifindex=0, netns_dev=makedev(0, 0), netns_ino=0, /* bytes 104..151 */ "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"}}}, 16) = 0
+bpf(BPF_OBJ_GET_INFO_BY_FD, {info={bpf_fd=4<anon_inode:bpf-prog>, info_len=152, info={type=BPF_PROG_TYPE_SOCKET_FILTER, id=8, tag="\xde\x90\x83\x18\xfb\x16\xd8\x9c", jited_prog_len=0, jited_prog_insns=NULL, xlated_prog_len=0, xlated_prog_insns=[], load_time=28281352029, created_by_uid=1000, nr_map_ids=2 => 1, map_ids=[15], name="test_prog", ifindex=0, netns_dev=makedev(0, 0), netns_ino=0, /* bytes 104..151 */ "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"}}}, 16) = 0
 +++ exited with 0 +++
bpf-obj_get_info_by_fd-prog-v.gen.test: failed test: ../../strace -a20 -y -v -e trace=bpf ../bpf-obj_get_info_by_fd-prog-v output mismatch
FAIL bpf-obj_get_info_by_fd-prog-v.gen.test (exit status: 1)