bpf: mark a NULL kfunc argument precisegrafted

check_kfunc_arg() allows bpf_register_is_null() for nullable arguments
w/o marking the underlying scalar register precise. Hence a checkpoint
created on such a path would prune against arbitrary scalar value.

Fixes: 3bda08b63670 ("bpf: Allow NULL buffers in bpf_dynptr_slice(_rw)")
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260904-register-is-null-precise-fixes-v1-5-0f5a360ff15d@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 154 insertions, 0 deletions

diff --git a/fs/compat_binfmt_elf.c b/fs/compat_binfmt_elf.c
new file mode 100644
index 000000000..d5ef5469e
--- /dev/null
+++ b/fs/compat_binfmt_elf.c
@@ -0,0 +1,154 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * 32-bit compatibility support for ELF format executables and core dumps.
+ *
+ * Copyright (C) 2007 Red Hat, Inc.  All rights reserved.
+ *
+ * Red Hat Author: Roland McGrath.
+ *
+ * This file is used in a 64-bit kernel that wants to support 32-bit ELF.
+ * asm/elf.h is responsible for defining the compat_* and COMPAT_* macros
+ * used below, with definitions appropriate for 32-bit ABI compatibility.
+ *
+ * We use macros to rename the ABI types and machine-dependent
+ * functions used in binfmt_elf.c to compat versions.
+ */
+
+#include <linux/elfcore-compat.h>
+#include <linux/time.h>
+
+#define ELF_COMPAT	1
+
+/*
+ * Rename the basic ELF layout types to refer to the 32-bit class of files.
+ */
+#undef	ELF_CLASS
+#define ELF_CLASS	ELFCLASS32
+
+#undef	elfhdr
+#undef	elf_phdr
+#undef	elf_shdr
+#undef	elf_note
+#undef	elf_addr_t
+#undef	ELF_GNU_PROPERTY_ALIGN
+#define elfhdr		elf32_hdr
+#define elf_phdr	elf32_phdr
+#define elf_shdr	elf32_shdr
+#define elf_note	elf32_note
+#define elf_addr_t	Elf32_Addr
+#define ELF_GNU_PROPERTY_ALIGN	ELF32_GNU_PROPERTY_ALIGN
+
+/*
+ * Some data types as stored in coredump.
+ */
+#define user_long_t		compat_long_t
+#define user_siginfo_t		compat_siginfo_t
+#define copy_siginfo_to_external	copy_siginfo_to_external32
+
+/*
+ * The machine-dependent core note format types are defined in elfcore-compat.h,
+ * which requires asm/elf.h to define compat_elf_gregset_t et al.
+ */
+#define elf_prstatus	compat_elf_prstatus
+#define elf_prstatus_common	compat_elf_prstatus_common
+#define elf_prpsinfo	compat_elf_prpsinfo
+
+#undef ns_to_kernel_old_timeval
+#define ns_to_kernel_old_timeval ns_to_old_timeval32
+
+/*
+ * To use this file, asm/elf.h must define compat_elf_check_arch.
+ * The other following macros can be defined if the compat versions
+ * differ from the native ones, or omitted when they match.
+ */
+
+#undef	elf_check_arch
+#define	elf_check_arch	compat_elf_check_arch
+
+#ifdef	COMPAT_ELF_PLATFORM
+#undef	ELF_PLATFORM
+#define	ELF_PLATFORM		COMPAT_ELF_PLATFORM
+#endif
+
+#ifdef	COMPAT_ELF_HWCAP
+#undef	ELF_HWCAP
+#define	ELF_HWCAP		COMPAT_ELF_HWCAP
+#endif
+
+#ifdef	COMPAT_ELF_HWCAP2
+#undef	ELF_HWCAP2
+#define	ELF_HWCAP2		COMPAT_ELF_HWCAP2
+#endif
+
+#ifdef	COMPAT_ELF_HWCAP3
+#undef	ELF_HWCAP3
+#define	ELF_HWCAP3		COMPAT_ELF_HWCAP3
+#endif
+
+#ifdef	COMPAT_ELF_HWCAP4
+#undef	ELF_HWCAP4
+#define	ELF_HWCAP4		COMPAT_ELF_HWCAP4
+#endif
+
+#ifdef	COMPAT_ARCH_DLINFO
+#undef	ARCH_DLINFO
+#define	ARCH_DLINFO		COMPAT_ARCH_DLINFO
+#endif
+
+#ifdef	COMPAT_ELF_ET_DYN_BASE
+#undef	ELF_ET_DYN_BASE
+#define	ELF_ET_DYN_BASE		COMPAT_ELF_ET_DYN_BASE
+#endif
+
+#ifdef	COMPAT_ELF_PLAT_INIT
+#undef	ELF_PLAT_INIT
+#define	ELF_PLAT_INIT		COMPAT_ELF_PLAT_INIT
+#endif
+
+#ifdef	COMPAT_SET_PERSONALITY
+#undef	SET_PERSONALITY
+#define	SET_PERSONALITY		COMPAT_SET_PERSONALITY
+#endif
+
+#ifdef	compat_start_thread
+#define COMPAT_START_THREAD(ex, regs, new_ip, new_sp)	\
+	compat_start_thread(regs, new_ip, new_sp)
+#endif
+
+#ifdef	COMPAT_START_THREAD
+#undef	START_THREAD
+#define START_THREAD		COMPAT_START_THREAD
+#endif
+
+#ifdef compat_arch_setup_additional_pages
+#define COMPAT_ARCH_SETUP_ADDITIONAL_PAGES(bprm, ex, interpreter) \
+	compat_arch_setup_additional_pages(bprm, interpreter)
+#endif
+
+#ifdef	COMPAT_ARCH_SETUP_ADDITIONAL_PAGES
+#undef	ARCH_HAS_SETUP_ADDITIONAL_PAGES
+#define ARCH_HAS_SETUP_ADDITIONAL_PAGES 1
+#undef	ARCH_SETUP_ADDITIONAL_PAGES
+#define	ARCH_SETUP_ADDITIONAL_PAGES COMPAT_ARCH_SETUP_ADDITIONAL_PAGES
+#endif
+
+#ifdef	compat_elf_read_implies_exec
+#undef	elf_read_implies_exec
+#define	elf_read_implies_exec compat_elf_read_implies_exec
+#endif
+
+/*
+ * Rename a few of the symbols that binfmt_elf.c will define.
+ * These are all local so the names don't really matter, but it
+ * might make some debugging less confusing not to duplicate them.
+ */
+#define elf_format		compat_elf_format
+#define init_elf_binfmt		init_compat_elf_binfmt
+#define exit_elf_binfmt		exit_compat_elf_binfmt
+#define binfmt_elf_test_cases	compat_binfmt_elf_test_cases
+#define binfmt_elf_test_suite	compat_binfmt_elf_test_suite
+
+/*
+ * We share all the actual code with the native (64-bit) version.
+ */
+#include "binfmt_elf.c"