Merge tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf

Daniel Borkmann says:

====================
pull-request: bpf 2024-06-14

We've added 8 non-merge commits during the last 2 day(s) which contain
a total of 9 files changed, 92 insertions(+), 11 deletions(-).

The main changes are:

1) Silence a syzkaller splat under CONFIG_DEBUG_NET=y in pskb_pull_reason()
   triggered via __bpf_try_make_writable(), from Florian Westphal.

2) Fix removal of kfuncs during linking phase which then throws a kernel
   build warning via resolve_btfids about unresolved symbols,
   from Tony Ambardar.

3) Fix a UML x86_64 compilation failure from BPF as pcpu_hot symbol
   is not available on User Mode Linux, from Maciej Żenczykowski.

4) Fix a register corruption in reg_set_min_max triggering an invariant
   violation in BPF verifier, from Daniel Borkmann.

* tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf:
  bpf: Harden __bpf_kfunc tag against linker kfunc removal
  compiler_types.h: Define __retain for __attribute__((__retain__))
  bpf: Avoid splat in pskb_pull_reason
  bpf: fix UML x86_64 compile failure
  selftests/bpf: Add test coverage for reg_set_min_max handling
  bpf: Reduce stack consumption in check_stack_write_fixed_off
  bpf: Fix reg_set_min_max corruption of fake_reg
  MAINTAINERS: mailmap: Update Stanislav's email address
====================

Link: https://lore.kernel.org/r/20240614203223.26500-1-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 16 insertions, 9 deletions

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 36ef8e96787e..010cfee7ffe9 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4549,11 +4549,12 @@ static int check_stack_write_fixed_off(struct bpf_verifier_env *env,
 			state->stack[spi].spilled_ptr.id = 0;
 	} else if (!reg && !(off % BPF_REG_SIZE) && is_bpf_st_mem(insn) &&
 		   env->bpf_capable) {
-		struct bpf_reg_state fake_reg = {};
+		struct bpf_reg_state *tmp_reg = &env->fake_reg[0];
 
-		__mark_reg_known(&fake_reg, insn->imm);
-		fake_reg.type = SCALAR_VALUE;
-		save_register_state(env, state, spi, &fake_reg, size);
+		memset(tmp_reg, 0, sizeof(*tmp_reg));
+		__mark_reg_known(tmp_reg, insn->imm);
+		tmp_reg->type = SCALAR_VALUE;
+		save_register_state(env, state, spi, tmp_reg, size);
 	} else if (reg && is_spillable_regtype(reg->type)) {
 		/* register containing pointer is being spilled into stack */
 		if (size != BPF_REG_SIZE) {
@@ -15113,7 +15114,6 @@ static int check_cond_jmp_op(struct bpf_verifier_env *env,
 	struct bpf_reg_state *regs = this_branch->frame[this_branch->curframe]->regs;
 	struct bpf_reg_state *dst_reg, *other_branch_regs, *src_reg = NULL;
 	struct bpf_reg_state *eq_branch_regs;
-	struct bpf_reg_state fake_reg = {};
 	u8 opcode = BPF_OP(insn->code);
 	bool is_jmp32;
 	int pred = -1;
@@ -15179,7 +15179,8 @@ static int check_cond_jmp_op(struct bpf_verifier_env *env,
 			verbose(env, "BPF_JMP/JMP32 uses reserved fields\n");
 			return -EINVAL;
 		}
-		src_reg = &fake_reg;
+		src_reg = &env->fake_reg[0];
+		memset(src_reg, 0, sizeof(*src_reg));
 		src_reg->type = SCALAR_VALUE;
 		__mark_reg_known(src_reg, insn->imm);
 	}
@@ -15239,10 +15240,16 @@ static int check_cond_jmp_op(struct bpf_verifier_env *env,
 				      &other_branch_regs[insn->src_reg],
 				      dst_reg, src_reg, opcode, is_jmp32);
 	} else /* BPF_SRC(insn->code) == BPF_K */ {
+		/* reg_set_min_max() can mangle the fake_reg. Make a copy
+		 * so that these are two different memory locations. The
+		 * src_reg is not used beyond here in context of K.
+		 */
+		memcpy(&env->fake_reg[1], &env->fake_reg[0],
+		       sizeof(env->fake_reg[0]));
 		err = reg_set_min_max(env,
 				      &other_branch_regs[insn->dst_reg],
-				      src_reg /* fake one */,
-				      dst_reg, src_reg /* same fake one */,
+				      &env->fake_reg[0],
+				      dst_reg, &env->fake_reg[1],
 				      opcode, is_jmp32);
 	}
 	if (err)
@@ -20313,7 +20320,7 @@ patch_map_ops_generic:
 			goto next_insn;
 		}
 
-#ifdef CONFIG_X86_64
+#if defined(CONFIG_X86_64) && !defined(CONFIG_UML)
 		/* Implement bpf_get_smp_processor_id() inline. */
 		if (insn->imm == BPF_FUNC_get_smp_processor_id &&
 		    prog->jit_requested && bpf_jit_supports_percpu_insn()) {