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Message-Id: <20210611180242.711399-2-dima@arista.com>
Date: Fri, 11 Jun 2021 19:02:20 +0100
From: Dmitry Safonov <dima@...sta.com>
To: linux-kernel@...r.kernel.org
Cc: Dmitry Safonov <0x7f454c46@...il.com>,
Dmitry Safonov <dima@...sta.com>,
Alexander Viro <viro@...iv.linux.org.uk>,
Andrew Morton <akpm@...ux-foundation.org>,
Andy Lutomirski <luto@...nel.org>,
Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
Catalin Marinas <catalin.marinas@....com>,
Christophe Leroy <christophe.leroy@...roup.eu>,
Guo Ren <guoren@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
Ingo Molnar <mingo@...hat.com>,
Oleg Nesterov <oleg@...hat.com>,
Russell King <linux@...linux.org.uk>,
Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
Thomas Gleixner <tglx@...utronix.de>,
Vincenzo Frascino <vincenzo.frascino@....com>,
Will Deacon <will@...nel.org>, x86@...nel.org
Subject: [PATCH v3 01/23] x86/elf: Check in_x32_syscall() in compat_arch_setup_additional_pages()
Partly revert commit 3316ec8ccd34 ("x86/elf: Use e_machine to check for
x32/ia32 in setup_additional_pages()") and commit 9a29a671902c ("elf:
Expose ELF header on arch_setup_additional_pages()".
Both patches did a good thing: removed usage of TIF_X32, but with
a price of additional macros ARCH_SETUP_ADDITIONAL_PAGES() and ifdeffs.
Instead, use in_x32_syscall() - the first thing load_elf_binary() does
after parsing and checking new ELF binary. It's done that early after
exec() that mmap() code already uses it straight away, which is needed
to know which mmap_base to use (see arch_pick_mmap_layout()).
Add comments to describe how it works.
Cc: x86@...nel.org
Signed-off-by: Dmitry Safonov <dima@...sta.com>
---
arch/x86/entry/vdso/vma.c | 4 ++--
arch/x86/include/asm/compat.h | 6 ++++++
arch/x86/include/asm/elf.h | 6 ++----
fs/binfmt_elf.c | 10 +++++++---
fs/compat_binfmt_elf.c | 11 +++--------
include/linux/elf.h | 5 -----
6 files changed, 20 insertions(+), 22 deletions(-)
diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index 235a5794296a..43d42ce82e86 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -396,10 +396,10 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
#ifdef CONFIG_COMPAT
int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
- int uses_interp, bool x32)
+ int uses_interp)
{
#ifdef CONFIG_X86_X32_ABI
- if (x32) {
+ if (in_x32_syscall()) {
if (!vdso64_enabled)
return 0;
return map_vdso_randomized(&vdso_image_x32);
diff --git a/arch/x86/include/asm/compat.h b/arch/x86/include/asm/compat.h
index be09c7eac89f..58f76665042c 100644
--- a/arch/x86/include/asm/compat.h
+++ b/arch/x86/include/asm/compat.h
@@ -186,6 +186,12 @@ static inline bool in_x32_syscall(void)
return false;
}
+/*
+ * Valid all the time on the context of a process that performs syscall.
+ * Just exec()ed process has __X32_SYSCALL_BIT or TS_COMPAT set very
+ * early in load_binary() on setting personality and flags.
+ * See also set_personality_ia32().
+ */
static inline bool in_32bit_syscall(void)
{
return in_ia32_syscall() || in_x32_syscall();
diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index 7d7500806af8..c0b5733005af 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -383,10 +383,8 @@ struct linux_binprm;
extern int arch_setup_additional_pages(struct linux_binprm *bprm,
int uses_interp);
extern int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
- int uses_interp, bool x32);
-#define COMPAT_ARCH_SETUP_ADDITIONAL_PAGES(bprm, ex, interpreter) \
- compat_arch_setup_additional_pages(bprm, interpreter, \
- (ex->e_machine == EM_X86_64))
+ int uses_interp);
+#define compat_arch_setup_additional_pages compat_arch_setup_additional_pages
extern bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs);
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 187b3f2b9202..2347d9067df6 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1002,8 +1002,12 @@ static int load_elf_binary(struct linux_binprm *bprm)
if (retval)
goto out_free_dentry;
- /* Do this immediately, since STACK_TOP as used in setup_arg_pages
- may depend on the personality. */
+ /*
+ * Do this immediately, since STACK_TOP as used in setup_arg_pages
+ * may depend on the personality. At this moment sys_exec()
+ * for loaded compatible application becomes non-native syscall
+ * and in_compat_syscall() starts working.
+ */
SET_PERSONALITY2(*elf_ex, &arch_state);
if (elf_read_implies_exec(*elf_ex, executable_stack))
current->personality |= READ_IMPLIES_EXEC;
@@ -1249,7 +1253,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
set_binfmt(&elf_format);
#ifdef ARCH_HAS_SETUP_ADDITIONAL_PAGES
- retval = ARCH_SETUP_ADDITIONAL_PAGES(bprm, elf_ex, !!interpreter);
+ retval = arch_setup_additional_pages(bprm, !!interpreter);
if (retval < 0)
goto out;
#endif /* ARCH_HAS_SETUP_ADDITIONAL_PAGES */
diff --git a/fs/compat_binfmt_elf.c b/fs/compat_binfmt_elf.c
index 95e72d271b95..049ba7c011b9 100644
--- a/fs/compat_binfmt_elf.c
+++ b/fs/compat_binfmt_elf.c
@@ -110,16 +110,11 @@
#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
+#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
+#undef arch_setup_additional_pages
+#define arch_setup_additional_pages compat_arch_setup_additional_pages
#endif
#ifdef compat_elf_read_implies_exec
diff --git a/include/linux/elf.h b/include/linux/elf.h
index c9a46c4e183b..6dbcfe7a3fd7 100644
--- a/include/linux/elf.h
+++ b/include/linux/elf.h
@@ -27,11 +27,6 @@
start_thread(regs, elf_entry, start_stack)
#endif
-#if defined(ARCH_HAS_SETUP_ADDITIONAL_PAGES) && !defined(ARCH_SETUP_ADDITIONAL_PAGES)
-#define ARCH_SETUP_ADDITIONAL_PAGES(bprm, ex, interpreter) \
- arch_setup_additional_pages(bprm, interpreter)
-#endif
-
#define ELF32_GNU_PROPERTY_ALIGN 4
#define ELF64_GNU_PROPERTY_ALIGN 8
--
2.31.1
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