From 18acb7fac22ff7b36c7ea5a76b12996e7b7dbaba Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 3 Nov 2022 13:00:13 +0100 Subject: bpf: Revert ("Fix dispatcher patchable function entry to 5 bytes nop") MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Because __attribute__((patchable_function_entry)) is only available since GCC-8 this solution fails to build on the minimum required GCC version. Undo these changes so we might try again -- without cluttering up the patches with too many changes. This is an almost complete revert of: dbe69b299884 ("bpf: Fix dispatcher patchable function entry to 5 bytes nop") ceea991a019c ("bpf: Move bpf_dispatcher function out of ftrace locations") (notably the arch/x86/Kconfig hunk is kept). Reported-by: David Laight Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Daniel Borkmann Tested-by: Björn Töpel Tested-by: Jiri Olsa Acked-by: Björn Töpel Acked-by: Jiri Olsa Link: https://lkml.kernel.org/r/439d8dc735bb4858875377df67f1b29a@AcuMS.aculab.com Link: https://lore.kernel.org/bpf/20221103120647.728830733@infradead.org --- kernel/bpf/dispatcher.c | 6 ------ 1 file changed, 6 deletions(-) (limited to 'kernel') diff --git a/kernel/bpf/dispatcher.c b/kernel/bpf/dispatcher.c index 04f0a045dcaa..fa64b80b8bca 100644 --- a/kernel/bpf/dispatcher.c +++ b/kernel/bpf/dispatcher.c @@ -4,7 +4,6 @@ #include #include #include -#include /* The BPF dispatcher is a multiway branch code generator. The * dispatcher is a mechanism to avoid the performance penalty of an @@ -91,11 +90,6 @@ int __weak arch_prepare_bpf_dispatcher(void *image, void *buf, s64 *funcs, int n return -ENOTSUPP; } -int __weak __init bpf_arch_init_dispatcher_early(void *ip) -{ - return -ENOTSUPP; -} - static int bpf_dispatcher_prepare(struct bpf_dispatcher *d, void *image, void *buf) { s64 ips[BPF_DISPATCHER_MAX] = {}, *ipsp = &ips[0]; -- cgit v1.2.3 From c86df29d11dfba27c0a1f5039cd6fe387fbf4239 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 3 Nov 2022 13:00:14 +0100 Subject: bpf: Convert BPF_DISPATCHER to use static_call() (not ftrace) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The dispatcher function is currently abusing the ftrace __fentry__ call location for its own purposes -- this obviously gives trouble when the dispatcher and ftrace are both in use. A previous solution tried using __attribute__((patchable_function_entry())) which works, except it is GCC-8+ only, breaking the build on the earlier still supported compilers. Instead use static_call() -- which has its own annotations and does not conflict with ftrace -- to rewrite the dispatch function. By using: return static_call()(ctx, insni, bpf_func) you get a perfect forwarding tail call as function body (iow a single jmp instruction). By having the default static_call() target be bpf_dispatcher_nop_func() it retains the default behaviour (an indirect call to the argument function). Only once a dispatcher program is attached is the target rewritten to directly call the JIT'ed image. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Daniel Borkmann Tested-by: Björn Töpel Tested-by: Jiri Olsa Acked-by: Björn Töpel Acked-by: Jiri Olsa Link: https://lkml.kernel.org/r/Y1/oBlK0yFk5c/Im@hirez.programming.kicks-ass.net Link: https://lore.kernel.org/bpf/20221103120647.796772565@infradead.org --- include/linux/bpf.h | 39 ++++++++++++++++++++++++++++++++++++++- kernel/bpf/dispatcher.c | 22 ++++++++-------------- 2 files changed, 46 insertions(+), 15 deletions(-) (limited to 'kernel') diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 5cd95716b441..74c6f449d81e 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -27,6 +27,7 @@ #include #include #include +#include struct bpf_verifier_env; struct bpf_verifier_log; @@ -953,6 +954,10 @@ struct bpf_dispatcher { void *rw_image; u32 image_off; struct bpf_ksym ksym; +#ifdef CONFIG_HAVE_STATIC_CALL + struct static_call_key *sc_key; + void *sc_tramp; +#endif }; static __always_inline __nocfi unsigned int bpf_dispatcher_nop_func( @@ -970,6 +975,34 @@ struct bpf_trampoline *bpf_trampoline_get(u64 key, struct bpf_attach_target_info *tgt_info); void bpf_trampoline_put(struct bpf_trampoline *tr); int arch_prepare_bpf_dispatcher(void *image, void *buf, s64 *funcs, int num_funcs); + +/* + * When the architecture supports STATIC_CALL replace the bpf_dispatcher_fn + * indirection with a direct call to the bpf program. If the architecture does + * not have STATIC_CALL, avoid a double-indirection. + */ +#ifdef CONFIG_HAVE_STATIC_CALL + +#define __BPF_DISPATCHER_SC_INIT(_name) \ + .sc_key = &STATIC_CALL_KEY(_name), \ + .sc_tramp = STATIC_CALL_TRAMP_ADDR(_name), + +#define __BPF_DISPATCHER_SC(name) \ + DEFINE_STATIC_CALL(bpf_dispatcher_##name##_call, bpf_dispatcher_nop_func) + +#define __BPF_DISPATCHER_CALL(name) \ + static_call(bpf_dispatcher_##name##_call)(ctx, insnsi, bpf_func) + +#define __BPF_DISPATCHER_UPDATE(_d, _new) \ + __static_call_update((_d)->sc_key, (_d)->sc_tramp, (_new)) + +#else +#define __BPF_DISPATCHER_SC_INIT(name) +#define __BPF_DISPATCHER_SC(name) +#define __BPF_DISPATCHER_CALL(name) bpf_func(ctx, insnsi) +#define __BPF_DISPATCHER_UPDATE(_d, _new) +#endif + #define BPF_DISPATCHER_INIT(_name) { \ .mutex = __MUTEX_INITIALIZER(_name.mutex), \ .func = &_name##_func, \ @@ -981,25 +1014,29 @@ int arch_prepare_bpf_dispatcher(void *image, void *buf, s64 *funcs, int num_func .name = #_name, \ .lnode = LIST_HEAD_INIT(_name.ksym.lnode), \ }, \ + __BPF_DISPATCHER_SC_INIT(_name##_call) \ } #define DEFINE_BPF_DISPATCHER(name) \ + __BPF_DISPATCHER_SC(name); \ noinline __nocfi unsigned int bpf_dispatcher_##name##_func( \ const void *ctx, \ const struct bpf_insn *insnsi, \ bpf_func_t bpf_func) \ { \ - return bpf_func(ctx, insnsi); \ + return __BPF_DISPATCHER_CALL(name); \ } \ EXPORT_SYMBOL(bpf_dispatcher_##name##_func); \ struct bpf_dispatcher bpf_dispatcher_##name = \ BPF_DISPATCHER_INIT(bpf_dispatcher_##name); + #define DECLARE_BPF_DISPATCHER(name) \ unsigned int bpf_dispatcher_##name##_func( \ const void *ctx, \ const struct bpf_insn *insnsi, \ bpf_func_t bpf_func); \ extern struct bpf_dispatcher bpf_dispatcher_##name; + #define BPF_DISPATCHER_FUNC(name) bpf_dispatcher_##name##_func #define BPF_DISPATCHER_PTR(name) (&bpf_dispatcher_##name) void bpf_dispatcher_change_prog(struct bpf_dispatcher *d, struct bpf_prog *from, diff --git a/kernel/bpf/dispatcher.c b/kernel/bpf/dispatcher.c index fa64b80b8bca..7dfb8d0d5202 100644 --- a/kernel/bpf/dispatcher.c +++ b/kernel/bpf/dispatcher.c @@ -4,6 +4,7 @@ #include #include #include +#include /* The BPF dispatcher is a multiway branch code generator. The * dispatcher is a mechanism to avoid the performance penalty of an @@ -104,17 +105,11 @@ static int bpf_dispatcher_prepare(struct bpf_dispatcher *d, void *image, void *b static void bpf_dispatcher_update(struct bpf_dispatcher *d, int prev_num_progs) { - void *old, *new, *tmp; - u32 noff; - int err; - - if (!prev_num_progs) { - old = NULL; - noff = 0; - } else { - old = d->image + d->image_off; + void *new, *tmp; + u32 noff = 0; + + if (prev_num_progs) noff = d->image_off ^ (PAGE_SIZE / 2); - } new = d->num_progs ? d->image + noff : NULL; tmp = d->num_progs ? d->rw_image + noff : NULL; @@ -128,11 +123,10 @@ static void bpf_dispatcher_update(struct bpf_dispatcher *d, int prev_num_progs) return; } - err = bpf_arch_text_poke(d->func, BPF_MOD_JUMP, old, new); - if (err || !new) - return; + __BPF_DISPATCHER_UPDATE(d, new ?: &bpf_dispatcher_nop_func); - d->image_off = noff; + if (new) + d->image_off = noff; } void bpf_dispatcher_change_prog(struct bpf_dispatcher *d, struct bpf_prog *from, -- cgit v1.2.3 From a679120edfcf3d63f066f53afd425d51b480e533 Mon Sep 17 00:00:00 2001 From: Nathan Chancellor Date: Mon, 7 Nov 2022 10:07:11 -0700 Subject: bpf: Add explicit cast to 'void *' for __BPF_DISPATCHER_UPDATE() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When building with clang: kernel/bpf/dispatcher.c:126:33: error: pointer type mismatch ('void *' and 'unsigned int (*)(const void *, const struct bpf_insn *, bpf_func_t)' (aka 'unsigned int (*)(const void *, const struct bpf_insn *, unsigned int (*)(const void *, const struct bpf_insn *))')) [-Werror,-Wpointer-type-mismatch] __BPF_DISPATCHER_UPDATE(d, new ?: &bpf_dispatcher_nop_func); ~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~ ./include/linux/bpf.h:1045:54: note: expanded from macro '__BPF_DISPATCHER_UPDATE' __static_call_update((_d)->sc_key, (_d)->sc_tramp, (_new)) ^~~~ 1 error generated. The warning is pointing out that the type of new ('void *') and &bpf_dispatcher_nop_func are not compatible, which could have side effects coming out of a conditional operator due to promotion rules. Add the explicit cast to 'void *' to make it clear that this is expected, as __BPF_DISPATCHER_UPDATE() expands to a call to __static_call_update(), which expects a 'void *' as its final argument. Fixes: c86df29d11df ("bpf: Convert BPF_DISPATCHER to use static_call() (not ftrace)") Link: https://github.com/ClangBuiltLinux/linux/issues/1755 Reported-by: kernel test robot Reported-by: "kernelci.org bot" Signed-off-by: Nathan Chancellor Acked-by: Björn Töpel Acked-by: Yonghong Song Link: https://lore.kernel.org/r/20221107170711.42409-1-nathan@kernel.org Signed-off-by: Martin KaFai Lau --- kernel/bpf/dispatcher.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel') diff --git a/kernel/bpf/dispatcher.c b/kernel/bpf/dispatcher.c index 7dfb8d0d5202..c19719f48ce0 100644 --- a/kernel/bpf/dispatcher.c +++ b/kernel/bpf/dispatcher.c @@ -123,7 +123,7 @@ static void bpf_dispatcher_update(struct bpf_dispatcher *d, int prev_num_progs) return; } - __BPF_DISPATCHER_UPDATE(d, new ?: &bpf_dispatcher_nop_func); + __BPF_DISPATCHER_UPDATE(d, new ?: (void *)&bpf_dispatcher_nop_func); if (new) d->image_off = noff; -- cgit v1.2.3 From eb86559a691cea5fa63e57a03ec3dc9c31e97955 Mon Sep 17 00:00:00 2001 From: Wang Yufen Date: Tue, 8 Nov 2022 13:11:31 +0800 Subject: bpf: Fix memory leaks in __check_func_call kmemleak reports this issue: unreferenced object 0xffff88817139d000 (size 2048): comm "test_progs", pid 33246, jiffies 4307381979 (age 45851.820s) hex dump (first 32 bytes): 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace: [<0000000045f075f0>] kmalloc_trace+0x27/0xa0 [<0000000098b7c90a>] __check_func_call+0x316/0x1230 [<00000000b4c3c403>] check_helper_call+0x172e/0x4700 [<00000000aa3875b7>] do_check+0x21d8/0x45e0 [<000000001147357b>] do_check_common+0x767/0xaf0 [<00000000b5a595b4>] bpf_check+0x43e3/0x5bc0 [<0000000011e391b1>] bpf_prog_load+0xf26/0x1940 [<0000000007f765c0>] __sys_bpf+0xd2c/0x3650 [<00000000839815d6>] __x64_sys_bpf+0x75/0xc0 [<00000000946ee250>] do_syscall_64+0x3b/0x90 [<0000000000506b7f>] entry_SYSCALL_64_after_hwframe+0x63/0xcd The root case here is: In function prepare_func_exit(), the callee is not released in the abnormal scenario after "state->curframe--;". To fix, move "state->curframe--;" to the very bottom of the function, right when we free callee and reset frame[] pointer to NULL, as Andrii suggested. In addition, function __check_func_call() has a similar problem. In the abnormal scenario before "state->curframe++;", the callee also should be released by free_func_state(). Fixes: 69c087ba6225 ("bpf: Add bpf_for_each_map_elem() helper") Fixes: fd978bf7fd31 ("bpf: Add reference tracking to verifier") Signed-off-by: Wang Yufen Link: https://lore.kernel.org/r/1667884291-15666-1-git-send-email-wangyufen@huawei.com Signed-off-by: Martin KaFai Lau --- kernel/bpf/verifier.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) (limited to 'kernel') diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 225666307bba..264b3dc714cc 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -6745,11 +6745,11 @@ static int __check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn /* Transfer references to the callee */ err = copy_reference_state(callee, caller); if (err) - return err; + goto err_out; err = set_callee_state_cb(env, caller, callee, *insn_idx); if (err) - return err; + goto err_out; clear_caller_saved_regs(env, caller->regs); @@ -6766,6 +6766,11 @@ static int __check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn print_verifier_state(env, callee, true); } return 0; + +err_out: + free_func_state(callee); + state->frame[state->curframe + 1] = NULL; + return err; } int map_set_for_each_callback_args(struct bpf_verifier_env *env, @@ -6979,8 +6984,7 @@ static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx) return -EINVAL; } - state->curframe--; - caller = state->frame[state->curframe]; + caller = state->frame[state->curframe - 1]; if (callee->in_callback_fn) { /* enforce R0 return value range [0, 1]. */ struct tnum range = callee->callback_ret_range; @@ -7019,7 +7023,7 @@ static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx) } /* clear everything in the callee */ free_func_state(callee); - state->frame[state->curframe + 1] = NULL; + state->frame[state->curframe--] = NULL; return 0; } -- cgit v1.2.3 From 4b45cd81f737d79d0fbfc0d320a1e518e7f0bbf0 Mon Sep 17 00:00:00 2001 From: Xu Kuohai Date: Thu, 10 Nov 2022 07:21:28 -0500 Subject: bpf: Initialize same number of free nodes for each pcpu_freelist pcpu_freelist_populate() initializes nr_elems / num_possible_cpus() + 1 free nodes for some CPUs, and then possibly one CPU with fewer nodes, followed by remaining cpus with 0 nodes. For example, when nr_elems == 256 and num_possible_cpus() == 32, CPU 0~27 each gets 9 free nodes, CPU 28 gets 4 free nodes, CPU 29~31 get 0 free nodes, while in fact each CPU should get 8 nodes equally. This patch initializes nr_elems / num_possible_cpus() free nodes for each CPU firstly, then allocates the remaining free nodes by one for each CPU until no free nodes left. Fixes: e19494edab82 ("bpf: introduce percpu_freelist") Signed-off-by: Xu Kuohai Signed-off-by: Andrii Nakryiko Acked-by: Yonghong Song Link: https://lore.kernel.org/bpf/20221110122128.105214-1-xukuohai@huawei.com --- kernel/bpf/percpu_freelist.c | 23 +++++++++++------------ 1 file changed, 11 insertions(+), 12 deletions(-) (limited to 'kernel') diff --git a/kernel/bpf/percpu_freelist.c b/kernel/bpf/percpu_freelist.c index b6e7f5c5b9ab..034cf87b54e9 100644 --- a/kernel/bpf/percpu_freelist.c +++ b/kernel/bpf/percpu_freelist.c @@ -100,22 +100,21 @@ void pcpu_freelist_populate(struct pcpu_freelist *s, void *buf, u32 elem_size, u32 nr_elems) { struct pcpu_freelist_head *head; - int i, cpu, pcpu_entries; + unsigned int cpu, cpu_idx, i, j, n, m; - pcpu_entries = nr_elems / num_possible_cpus() + 1; - i = 0; + n = nr_elems / num_possible_cpus(); + m = nr_elems % num_possible_cpus(); + cpu_idx = 0; for_each_possible_cpu(cpu) { -again: head = per_cpu_ptr(s->freelist, cpu); - /* No locking required as this is not visible yet. */ - pcpu_freelist_push_node(head, buf); - i++; - buf += elem_size; - if (i == nr_elems) - break; - if (i % pcpu_entries) - goto again; + j = n + (cpu_idx < m ? 1 : 0); + for (i = 0; i < j; i++) { + /* No locking required as this is not visible yet. */ + pcpu_freelist_push_node(head, buf); + buf += elem_size; + } + cpu_idx++; } } -- cgit v1.2.3