From: Xu Kuohai xukuohai@huawei.com

stable inclusion from stable-v6.6.57 commit 5d5e3b4cbe8ee16b7bf96fd73a421c92a9da3ca1 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAYRIC CVE: CVE-2024-50063

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...

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[ Upstream commit 28ead3eaabc16ecc907cfb71876da028080f6356 ]

bpf progs can be attached to kernel functions, and the attached functions can take different parameters or return different return values. If prog attached to one kernel function tail calls prog attached to another kernel function, the ctx access or return value verification could be bypassed.

For example, if prog1 is attached to func1 which takes only 1 parameter and prog2 is attached to func2 which takes two parameters. Since verifier assumes the bpf ctx passed to prog2 is constructed based on func2's prototype, verifier allows prog2 to access the second parameter from the bpf ctx passed to it. The problem is that verifier does not prevent prog1 from passing its bpf ctx to prog2 via tail call. In this case, the bpf ctx passed to prog2 is constructed from func1 instead of func2, that is, the assumption for ctx access verification is bypassed.

Another example, if BPF LSM prog1 is attached to hook file_alloc_security, and BPF LSM prog2 is attached to hook bpf_lsm_audit_rule_known. Verifier knows the return value rules for these two hooks, e.g. it is legal for bpf_lsm_audit_rule_known to return positive number 1, and it is illegal for file_alloc_security to return positive number. So verifier allows prog2 to return positive number 1, but does not allow prog1 to return positive number. The problem is that verifier does not prevent prog1 from calling prog2 via tail call. In this case, prog2's return value 1 will be used as the return value for prog1's hook file_alloc_security. That is, the return value rule is bypassed.

This patch adds restriction for tail call to prevent such bypasses.

Signed-off-by: Xu Kuohai xukuohai@huawei.com Link: https://lore.kernel.org/r/20240719110059.797546-4-xukuohai@huaweicloud.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Andrii Nakryiko andrii@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Pu Lehui pulehui@huawei.com --- include/linux/bpf.h | 1 + kernel/bpf/core.c | 21 ++++++++++++++++++--- 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h index abc920234c28..e295c1cec087 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -294,6 +294,7 @@ struct bpf_map { * same prog type, JITed flag and xdp_has_frags flag. */ struct { + const struct btf_type *attach_func_proto; spinlock_t lock; enum bpf_prog_type type; bool jited; diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index c68931013533..109110cabc4e 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -2259,6 +2259,7 @@ bool bpf_prog_map_compatible(struct bpf_map *map, { enum bpf_prog_type prog_type = resolve_prog_type(fp); bool ret; + struct bpf_prog_aux *aux = fp->aux;

if (fp->kprobe_override) return false; @@ -2268,7 +2269,7 @@ bool bpf_prog_map_compatible(struct bpf_map *map, * in the case of devmap and cpumap). Until device checks * are implemented, prohibit adding dev-bound programs to program maps. */ - if (bpf_prog_is_dev_bound(fp->aux)) + if (bpf_prog_is_dev_bound(aux)) return false;

spin_lock(&map->owner.lock); @@ -2278,12 +2279,26 @@ bool bpf_prog_map_compatible(struct bpf_map *map, */ map->owner.type = prog_type; map->owner.jited = fp->jited; - map->owner.xdp_has_frags = fp->aux->xdp_has_frags; + map->owner.xdp_has_frags = aux->xdp_has_frags; + map->owner.attach_func_proto = aux->attach_func_proto; ret = true; } else { ret = map->owner.type == prog_type && map->owner.jited == fp->jited && - map->owner.xdp_has_frags == fp->aux->xdp_has_frags; + map->owner.xdp_has_frags == aux->xdp_has_frags; + if (ret && + map->owner.attach_func_proto != aux->attach_func_proto) { + switch (prog_type) { + case BPF_PROG_TYPE_TRACING: + case BPF_PROG_TYPE_LSM: + case BPF_PROG_TYPE_EXT: + case BPF_PROG_TYPE_STRUCT_OPS: + ret = false; + break; + default: + break; + } + } } spin_unlock(&map->owner.lock);

From: Xu Kuohai xukuohai@huawei.com

mainline inclusion from mainline-v6.12-rc1 commit d463dd9c9aa24b17ccb8ed76bdd7768baf857b48 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAYRIC CVE: CVE-2024-50063

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...

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Add test for lsm tail call to ensure tail call can only be used between bpf lsm progs attached to the same hook.

Signed-off-by: Xu Kuohai xukuohai@huawei.com Link: https://lore.kernel.org/r/20240719110059.797546-9-xukuohai@huaweicloud.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Andrii Nakryiko andrii@kernel.org Signed-off-by: Pu Lehui pulehui@huawei.com --- .../selftests/bpf/prog_tests/test_lsm.c | 46 ++++++++++++++++++- .../selftests/bpf/progs/lsm_tailcall.c | 34 ++++++++++++++ 2 files changed, 79 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/bpf/progs/lsm_tailcall.c

diff --git a/tools/testing/selftests/bpf/prog_tests/test_lsm.c b/tools/testing/selftests/bpf/prog_tests/test_lsm.c index 16175d579bc7..2a27f3714f5c 100644 --- a/tools/testing/selftests/bpf/prog_tests/test_lsm.c +++ b/tools/testing/selftests/bpf/prog_tests/test_lsm.c @@ -12,6 +12,7 @@ #include <stdlib.h>

#include "lsm.skel.h" +#include "lsm_tailcall.skel.h"

char *CMD_ARGS[] = {"true", NULL};

@@ -95,7 +96,7 @@ static int test_lsm(struct lsm *skel) return 0; }

-void test_test_lsm(void) +static void test_lsm_basic(void) { struct lsm *skel = NULL; int err; @@ -114,3 +115,46 @@ void test_test_lsm(void) close_prog: lsm__destroy(skel); } + +static void test_lsm_tailcall(void) +{ + struct lsm_tailcall *skel = NULL; + int map_fd, prog_fd; + int err, key; + + skel = lsm_tailcall__open_and_load(); + if (!ASSERT_OK_PTR(skel, "lsm_tailcall__skel_load")) + goto close_prog; + + map_fd = bpf_map__fd(skel->maps.jmp_table); + if (CHECK_FAIL(map_fd < 0)) + goto close_prog; + + prog_fd = bpf_program__fd(skel->progs.lsm_file_permission_prog); + if (CHECK_FAIL(prog_fd < 0)) + goto close_prog; + + key = 0; + err = bpf_map_update_elem(map_fd, &key, &prog_fd, BPF_ANY); + if (CHECK_FAIL(!err)) + goto close_prog; + + prog_fd = bpf_program__fd(skel->progs.lsm_file_alloc_security_prog); + if (CHECK_FAIL(prog_fd < 0)) + goto close_prog; + + err = bpf_map_update_elem(map_fd, &key, &prog_fd, BPF_ANY); + if (CHECK_FAIL(err)) + goto close_prog; + +close_prog: + lsm_tailcall__destroy(skel); +} + +void test_test_lsm(void) +{ + if (test__start_subtest("lsm_basic")) + test_lsm_basic(); + if (test__start_subtest("lsm_tailcall")) + test_lsm_tailcall(); +} diff --git a/tools/testing/selftests/bpf/progs/lsm_tailcall.c b/tools/testing/selftests/bpf/progs/lsm_tailcall.c new file mode 100644 index 000000000000..49c075ce2d4c --- /dev/null +++ b/tools/testing/selftests/bpf/progs/lsm_tailcall.c @@ -0,0 +1,34 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2024 Huawei Technologies Co., Ltd */ + +#include "vmlinux.h" +#include <errno.h> +#include <bpf/bpf_helpers.h> + +char _license[] SEC("license") = "GPL"; + +struct { + __uint(type, BPF_MAP_TYPE_PROG_ARRAY); + __uint(max_entries, 1); + __uint(key_size, sizeof(__u32)); + __uint(value_size, sizeof(__u32)); +} jmp_table SEC(".maps"); + +SEC("lsm/file_permission") +int lsm_file_permission_prog(void *ctx) +{ + return 0; +} + +SEC("lsm/file_alloc_security") +int lsm_file_alloc_security_prog(void *ctx) +{ + return 0; +} + +SEC("lsm/file_alloc_security") +int lsm_file_alloc_security_entry(void *ctx) +{ + bpf_tail_call_static(ctx, &jmp_table, 0); + return 0; +}