On March 21, 2017 9:37:12 AM PDT, Dmitry Safonov <[email protected]> wrote: >After my changes to mmap(), its code now relies on the bitness of >performing syscall. According to that, it chooses the base of >allocation: >mmap_base for 64-bit mmap() and mmap_compat_base for 32-bit syscall. >It was done by: > commit 1b028f784e8c ("x86/mm: Introduce mmap_compat_base() for >32-bit mmap()"). > >The code afterwards relies on in_compat_syscall() returning true for >32-bit syscalls. It's usually so while we're in context of application >that does 32-bit syscalls. But during exec() it is not valid for x32 >ELF. >The reason is that the application hasn't yet done any syscall, so x32 >bit has not being set. >That results in -ENOMEM for x32 ELF files as there fired BAD_ADDR() >in elf_map(), that is called from do_execve()->load_elf_binary(). >For i386 ELFs it works as SET_PERSONALITY() sets TS_COMPAT flag. > >I suggest to set x32 bit before first return to userspace, during >setting personality at exec(). This way we can rely on >in_compat_syscall() during exec(). > >Fixes: commit 1b028f784e8c ("x86/mm: Introduce mmap_compat_base() for >32-bit mmap()") >Cc: [email protected] >Cc: [email protected] >Cc: Andrei Vagin <[email protected]> >Cc: Cyrill Gorcunov <[email protected]> >Cc: Borislav Petkov <[email protected]> >Cc: "Kirill A. Shutemov" <[email protected]> >Cc: [email protected] >Cc: H. Peter Anvin <[email protected]> >Cc: Andy Lutomirski <[email protected]> >Cc: Ingo Molnar <[email protected]> >Cc: Thomas Gleixner <[email protected]> >Reported-by: Adam Borowski <[email protected]> >Signed-off-by: Dmitry Safonov <[email protected]> >--- >v2: >- specifying mmap() allocation path which failed during exec() >- fix comment style > > arch/x86/kernel/process_64.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > >diff --git a/arch/x86/kernel/process_64.c >b/arch/x86/kernel/process_64.c >index d6b784a5520d..d3d4d9abcaf8 100644 >--- a/arch/x86/kernel/process_64.c >+++ b/arch/x86/kernel/process_64.c >@@ -519,8 +519,14 @@ void set_personality_ia32(bool x32) > if (current->mm) > current->mm->context.ia32_compat = TIF_X32; > current->personality &= ~READ_IMPLIES_EXEC; >- /* in_compat_syscall() uses the presence of the x32 >- syscall bit flag to determine compat status */ >+ /* >+ * in_compat_syscall() uses the presence of the x32 >+ * syscall bit flag to determine compat status. >+ * On the bitness of syscall relies x86 mmap() code, >+ * so set x32 syscall bit right here to make >+ * in_compat_syscall() work during exec(). >+ */ >+ task_pt_regs(current)->orig_ax |= __X32_SYSCALL_BIT; > current->thread.status &= ~TS_COMPAT; > } else { > set_thread_flag(TIF_IA32);
You also need to clear the bit for an x32 -> x86-64 exec. Otherwise it seems okay to me. -- Sent from my Android device with K-9 Mail. Please excuse my brevity.
