| Message ID | 20200207064741.5798-2-po-hsu.lin@canonical.com |
|---|---|
| State | New |
| Headers | show |
| Series | [Eoan,SRU,1/1] bpf: fix accessing bpf_sysctl.file_pos on s390 | expand |
Upstream commit, clean cherry-pick, test provided.
Acked-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
On 07/02/2020 06:47, Po-Hsu Lin wrote: > From: Ilya Leoshkevich <iii@linux.ibm.com> > > BugLink: https://bugs.launchpad.net/bugs/1862263 > > "ctx:file_pos sysctl:read write ok" fails on s390 with "Read value != > nux". This is because verifier rewrites a complete 32-bit > bpf_sysctl.file_pos update to a partial update of the first 32 bits of > 64-bit *bpf_sysctl_kern.ppos, which is not correct on big-endian > systems. > > Fix by using an offset on big-endian systems. > > Ditto for bpf_sysctl.file_pos reads. Currently the test does not detect > a problem there, since it expects to see 0, which it gets with high > probability in error cases, so change it to seek to offset 3 and expect > 3 in bpf_sysctl.file_pos. > > Fixes: e1550bfe0de4 ("bpf: Add file_pos field to bpf_sysctl ctx") > Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com> > Acked-by: Yonghong Song <yhs@fb.com> > Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> > Link: https://lore.kernel.org/bpf/20190816105300.49035-1-iii@linux.ibm.com/ > (cherry picked from commit d895a0f16fadb26d22ab531c49768f7642ae5c3e) > Signed-off-by: Po-Hsu Lin <po-hsu.lin@canonical.com> > --- > include/linux/filter.h | 8 ++++---- > kernel/bpf/cgroup.c | 10 ++++++++-- > kernel/bpf/verifier.c | 4 ++-- > tools/testing/selftests/bpf/test_sysctl.c | 9 ++++++++- > 4 files changed, 22 insertions(+), 9 deletions(-) > > diff --git a/include/linux/filter.h b/include/linux/filter.h > index 38716f9..0367a75 100644 > --- a/include/linux/filter.h > +++ b/include/linux/filter.h > @@ -749,14 +749,14 @@ bpf_ctx_narrow_access_ok(u32 off, u32 size, u32 size_default) > } > > static inline u8 > -bpf_ctx_narrow_load_shift(u32 off, u32 size, u32 size_default) > +bpf_ctx_narrow_access_offset(u32 off, u32 size, u32 size_default) > { > - u8 load_off = off & (size_default - 1); > + u8 access_off = off & (size_default - 1); > > #ifdef __LITTLE_ENDIAN > - return load_off * 8; > + return access_off; > #else > - return (size_default - (load_off + size)) * 8; > + return size_default - (access_off + size); > #endif > } > > diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c > index 9ad7cd3..521e341 100644 > --- a/kernel/bpf/cgroup.c > +++ b/kernel/bpf/cgroup.c > @@ -1325,6 +1325,7 @@ static u32 sysctl_convert_ctx_access(enum bpf_access_type type, > struct bpf_prog *prog, u32 *target_size) > { > struct bpf_insn *insn = insn_buf; > + u32 read_size; > > switch (si->off) { > case offsetof(struct bpf_sysctl, write): > @@ -1356,7 +1357,9 @@ static u32 sysctl_convert_ctx_access(enum bpf_access_type type, > treg, si->dst_reg, > offsetof(struct bpf_sysctl_kern, ppos)); > *insn++ = BPF_STX_MEM( > - BPF_SIZEOF(u32), treg, si->src_reg, 0); > + BPF_SIZEOF(u32), treg, si->src_reg, > + bpf_ctx_narrow_access_offset( > + 0, sizeof(u32), sizeof(loff_t))); > *insn++ = BPF_LDX_MEM( > BPF_DW, treg, si->dst_reg, > offsetof(struct bpf_sysctl_kern, tmp_reg)); > @@ -1365,8 +1368,11 @@ static u32 sysctl_convert_ctx_access(enum bpf_access_type type, > BPF_FIELD_SIZEOF(struct bpf_sysctl_kern, ppos), > si->dst_reg, si->src_reg, > offsetof(struct bpf_sysctl_kern, ppos)); > + read_size = bpf_size_to_bytes(BPF_SIZE(si->code)); > *insn++ = BPF_LDX_MEM( > - BPF_SIZE(si->code), si->dst_reg, si->dst_reg, 0); > + BPF_SIZE(si->code), si->dst_reg, si->dst_reg, > + bpf_ctx_narrow_access_offset( > + 0, read_size, sizeof(loff_t))); > } > *target_size = sizeof(u32); > break; > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > index 72161f5d..3c9f9c4 100644 > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -8641,8 +8641,8 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env) > } > > if (is_narrower_load && size < target_size) { > - u8 shift = bpf_ctx_narrow_load_shift(off, size, > - size_default); > + u8 shift = bpf_ctx_narrow_access_offset( > + off, size, size_default) * 8; > if (ctx_field_size <= 4) { > if (shift) > insn_buf[cnt++] = BPF_ALU32_IMM(BPF_RSH, > diff --git a/tools/testing/selftests/bpf/test_sysctl.c b/tools/testing/selftests/bpf/test_sysctl.c > index c938f17..70e2e96 100644 > --- a/tools/testing/selftests/bpf/test_sysctl.c > +++ b/tools/testing/selftests/bpf/test_sysctl.c > @@ -31,6 +31,7 @@ struct sysctl_test { > enum bpf_attach_type attach_type; > const char *sysctl; > int open_flags; > + int seek; > const char *newval; > const char *oldval; > enum { > @@ -139,7 +140,7 @@ static struct sysctl_test tests[] = { > /* If (file_pos == X) */ > BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_1, > offsetof(struct bpf_sysctl, file_pos)), > - BPF_JMP_IMM(BPF_JNE, BPF_REG_7, 0, 2), > + BPF_JMP_IMM(BPF_JNE, BPF_REG_7, 3, 2), > > /* return ALLOW; */ > BPF_MOV64_IMM(BPF_REG_0, 1), > @@ -152,6 +153,7 @@ static struct sysctl_test tests[] = { > .attach_type = BPF_CGROUP_SYSCTL, > .sysctl = "kernel/ostype", > .open_flags = O_RDONLY, > + .seek = 3, > .result = SUCCESS, > }, > { > @@ -1448,6 +1450,11 @@ static int access_sysctl(const char *sysctl_path, > if (fd < 0) > return fd; > > + if (test->seek && lseek(fd, test->seek, SEEK_SET) == -1) { > + log_err("lseek(%d) failed", test->seek); > + goto err; > + } > + > if (test->open_flags == O_RDONLY) { > char buf[128]; > > Upstream cherry pick with positive test results. LGTM, Acked-by: Colin Ian King <colin.king@canonical.com>
diff --git a/include/linux/filter.h b/include/linux/filter.h index 38716f9..0367a75 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -749,14 +749,14 @@ bpf_ctx_narrow_access_ok(u32 off, u32 size, u32 size_default) } static inline u8 -bpf_ctx_narrow_load_shift(u32 off, u32 size, u32 size_default) +bpf_ctx_narrow_access_offset(u32 off, u32 size, u32 size_default) { - u8 load_off = off & (size_default - 1); + u8 access_off = off & (size_default - 1); #ifdef __LITTLE_ENDIAN - return load_off * 8; + return access_off; #else - return (size_default - (load_off + size)) * 8; + return size_default - (access_off + size); #endif } diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c index 9ad7cd3..521e341 100644 --- a/kernel/bpf/cgroup.c +++ b/kernel/bpf/cgroup.c @@ -1325,6 +1325,7 @@ static u32 sysctl_convert_ctx_access(enum bpf_access_type type, struct bpf_prog *prog, u32 *target_size) { struct bpf_insn *insn = insn_buf; + u32 read_size; switch (si->off) { case offsetof(struct bpf_sysctl, write): @@ -1356,7 +1357,9 @@ static u32 sysctl_convert_ctx_access(enum bpf_access_type type, treg, si->dst_reg, offsetof(struct bpf_sysctl_kern, ppos)); *insn++ = BPF_STX_MEM( - BPF_SIZEOF(u32), treg, si->src_reg, 0); + BPF_SIZEOF(u32), treg, si->src_reg, + bpf_ctx_narrow_access_offset( + 0, sizeof(u32), sizeof(loff_t))); *insn++ = BPF_LDX_MEM( BPF_DW, treg, si->dst_reg, offsetof(struct bpf_sysctl_kern, tmp_reg)); @@ -1365,8 +1368,11 @@ static u32 sysctl_convert_ctx_access(enum bpf_access_type type, BPF_FIELD_SIZEOF(struct bpf_sysctl_kern, ppos), si->dst_reg, si->src_reg, offsetof(struct bpf_sysctl_kern, ppos)); + read_size = bpf_size_to_bytes(BPF_SIZE(si->code)); *insn++ = BPF_LDX_MEM( - BPF_SIZE(si->code), si->dst_reg, si->dst_reg, 0); + BPF_SIZE(si->code), si->dst_reg, si->dst_reg, + bpf_ctx_narrow_access_offset( + 0, read_size, sizeof(loff_t))); } *target_size = sizeof(u32); break; diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 72161f5d..3c9f9c4 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -8641,8 +8641,8 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env) } if (is_narrower_load && size < target_size) { - u8 shift = bpf_ctx_narrow_load_shift(off, size, - size_default); + u8 shift = bpf_ctx_narrow_access_offset( + off, size, size_default) * 8; if (ctx_field_size <= 4) { if (shift) insn_buf[cnt++] = BPF_ALU32_IMM(BPF_RSH, diff --git a/tools/testing/selftests/bpf/test_sysctl.c b/tools/testing/selftests/bpf/test_sysctl.c index c938f17..70e2e96 100644 --- a/tools/testing/selftests/bpf/test_sysctl.c +++ b/tools/testing/selftests/bpf/test_sysctl.c @@ -31,6 +31,7 @@ struct sysctl_test { enum bpf_attach_type attach_type; const char *sysctl; int open_flags; + int seek; const char *newval; const char *oldval; enum { @@ -139,7 +140,7 @@ static struct sysctl_test tests[] = { /* If (file_pos == X) */ BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_1, offsetof(struct bpf_sysctl, file_pos)), - BPF_JMP_IMM(BPF_JNE, BPF_REG_7, 0, 2), + BPF_JMP_IMM(BPF_JNE, BPF_REG_7, 3, 2), /* return ALLOW; */ BPF_MOV64_IMM(BPF_REG_0, 1), @@ -152,6 +153,7 @@ static struct sysctl_test tests[] = { .attach_type = BPF_CGROUP_SYSCTL, .sysctl = "kernel/ostype", .open_flags = O_RDONLY, + .seek = 3, .result = SUCCESS, }, { @@ -1448,6 +1450,11 @@ static int access_sysctl(const char *sysctl_path, if (fd < 0) return fd; + if (test->seek && lseek(fd, test->seek, SEEK_SET) == -1) { + log_err("lseek(%d) failed", test->seek); + goto err; + } + if (test->open_flags == O_RDONLY) { char buf[128];