x86/mm: Make in_compat_syscall() work during exec
The x86 mmap() code selects the mmap base for an allocation depending on
the bitness of the syscall. For 64bit sycalls it select mm->mmap_base and
for 32bit mm->mmap_compat_base.
On execve the registers of the task invoking exec() are copied to the child
pt_regs. So child->pt_regs->orig_ax contains the execve syscall number of the
parent.
exec() calls mmap() which in turn uses in_compat_syscall() to check whether
the mapping is for a 32bit or a 64bit task. The decision is made on the
following criteria:
ia32 child->thread.status & TS_COMPAT
x32 child->pt_regs.orig_ax & __X32_SYSCALL_BIT
ia64 !ia32 && !x32
child->thread.status is corretly set up in set_personality_*(), but the
syscall number in child->pt_regs.orig_ax is left unmodified.
Therefore the parent/child combinations work or fail in the following way:
Parent Child Child->thread_status child->pt_regs.orig_ax in_compat() Works
ia64 ia64 TS_COMPAT == 0 __X32_SYSCALL_BIT == 0 false Y
ia64 ia32 TS_COMPAT == 1 __X32_SYSCALL_BIT == 0 true Y
ia64 x32 TS_COMPAT == 0 __X32_SYSCALL_BIT == 0 false N
ia32 ia64 TS_COMPAT == 0 __X32_SYSCALL_BIT == 0 false Y
ia32 ia32 TS_COMPAT == 1 __X32_SYSCALL_BIT == 0 true Y
ia32 x32 TS_COMPAT == 0 __X32_SYSCALL_BIT == 0 false N
x32 ia64 TS_COMPAT == 0 __X32_SYSCALL_BIT == 1 true N
x32 ia32 TS_COMPAT == 1 __X32_SYSCALL_BIT == 1 true Y
x32 x32 TS_COMPAT == 0 __X32_SYSCALL_BIT == 1 true Y
Make set_personality_*() store the syscall number incl. __X32_SYSCALL_BIT
which corresponds to the newly started ELF executable in the childs
pt_regs, i.e. pretend that the exec was invoked from a task with the same
executable format.
So both thread.status and pt_regs.orig_ax correspond to the new ELF format
and in_compat_syscall() returns the correct result.
[ tglx: Rewrote changelog ]
Fixes: commit 1b028f784e
("x86/mm: Introduce mmap_compat_base() for 32-bit mmap()")
Reported-by: Adam Borowski <kilobyte@angband.pl>
Suggested-by: H. Peter Anvin <hpa@zytor.com>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Cc: 0x7f454c46@gmail.com
Cc: linux-mm@kvack.org
Cc: Andrei Vagin <avagin@gmail.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Link: http://lkml.kernel.org/r/20170331111137.28170-1-dsafonov@virtuozzo.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Родитель
952a6c2c09
Коммит
ada26481df
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@ -53,6 +53,11 @@
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#include <asm/xen/hypervisor.h>
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#include <asm/vdso.h>
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#include <asm/intel_rdt.h>
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#include <asm/unistd.h>
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#ifdef CONFIG_IA32_EMULATION
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/* Not included via unistd.h */
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#include <asm/unistd_32_ia32.h>
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#endif
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__visible DEFINE_PER_CPU(unsigned long, rsp_scratch);
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@ -494,6 +499,8 @@ void set_personality_64bit(void)
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clear_thread_flag(TIF_IA32);
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clear_thread_flag(TIF_ADDR32);
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clear_thread_flag(TIF_X32);
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/* Pretend that this comes from a 64bit execve */
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task_pt_regs(current)->orig_ax = __NR_execve;
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/* Ensure the corresponding mm is not marked. */
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if (current->mm)
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@ -506,32 +513,50 @@ void set_personality_64bit(void)
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current->personality &= ~READ_IMPLIES_EXEC;
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}
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static void __set_personality_x32(void)
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{
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#ifdef CONFIG_X86_X32
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clear_thread_flag(TIF_IA32);
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set_thread_flag(TIF_X32);
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if (current->mm)
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current->mm->context.ia32_compat = TIF_X32;
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current->personality &= ~READ_IMPLIES_EXEC;
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/*
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* in_compat_syscall() uses the presence of the x32 syscall bit
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* flag to determine compat status. The x86 mmap() code relies on
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* the syscall bitness so set x32 syscall bit right here to make
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* in_compat_syscall() work during exec().
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*
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* Pretend to come from a x32 execve.
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*/
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task_pt_regs(current)->orig_ax = __NR_x32_execve | __X32_SYSCALL_BIT;
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current->thread.status &= ~TS_COMPAT;
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#endif
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}
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static void __set_personality_ia32(void)
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{
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#ifdef CONFIG_IA32_EMULATION
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set_thread_flag(TIF_IA32);
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clear_thread_flag(TIF_X32);
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if (current->mm)
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current->mm->context.ia32_compat = TIF_IA32;
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current->personality |= force_personality32;
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/* Prepare the first "return" to user space */
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task_pt_regs(current)->orig_ax = __NR_ia32_execve;
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current->thread.status |= TS_COMPAT;
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#endif
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}
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void set_personality_ia32(bool x32)
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{
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/* inherit personality from parent */
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/* Make sure to be in 32bit mode */
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set_thread_flag(TIF_ADDR32);
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/* Mark the associated mm as containing 32-bit tasks. */
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if (x32) {
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clear_thread_flag(TIF_IA32);
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set_thread_flag(TIF_X32);
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if (current->mm)
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current->mm->context.ia32_compat = TIF_X32;
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current->personality &= ~READ_IMPLIES_EXEC;
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/* in_compat_syscall() uses the presence of the x32
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syscall bit flag to determine compat status */
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current->thread.status &= ~TS_COMPAT;
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} else {
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set_thread_flag(TIF_IA32);
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clear_thread_flag(TIF_X32);
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if (current->mm)
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current->mm->context.ia32_compat = TIF_IA32;
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current->personality |= force_personality32;
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/* Prepare the first "return" to user space */
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current->thread.status |= TS_COMPAT;
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}
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if (x32)
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__set_personality_x32();
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else
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__set_personality_ia32();
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}
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EXPORT_SYMBOL_GPL(set_personality_ia32);
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