diff options
Diffstat (limited to 'target/linux/generic/backport-4.9/096-mips-math-emu-Write-protect-delay-slot-emulation-pages.patch')
| -rw-r--r-- | target/linux/generic/backport-4.9/096-mips-math-emu-Write-protect-delay-slot-emulation-pages.patch | 119 |
1 files changed, 0 insertions, 119 deletions
diff --git a/target/linux/generic/backport-4.9/096-mips-math-emu-Write-protect-delay-slot-emulation-pages.patch b/target/linux/generic/backport-4.9/096-mips-math-emu-Write-protect-delay-slot-emulation-pages.patch deleted file mode 100644 index 69cc493bba..0000000000 --- a/target/linux/generic/backport-4.9/096-mips-math-emu-Write-protect-delay-slot-emulation-pages.patch +++ /dev/null @@ -1,119 +0,0 @@ -From adcc81f148d733b7e8e641300c5590a2cdc13bf3 Mon Sep 17 00:00:00 2001 -From: Paul Burton <paul.burton@mips.com> -Date: Thu, 20 Dec 2018 17:45:43 +0000 -Subject: MIPS: math-emu: Write-protect delay slot emulation pages - -Mapping the delay slot emulation page as both writeable & executable -presents a security risk, in that if an exploit can write to & jump into -the page then it can be used as an easy way to execute arbitrary code. - -Prevent this by mapping the page read-only for userland, and using -access_process_vm() with the FOLL_FORCE flag to write to it from -mips_dsemul(). - -This will likely be less efficient due to copy_to_user_page() performing -cache maintenance on a whole page, rather than a single line as in the -previous use of flush_cache_sigtramp(). However this delay slot -emulation code ought not to be running in any performance critical paths -anyway so this isn't really a problem, and we can probably do better in -copy_to_user_page() anyway in future. - -A major advantage of this approach is that the fix is small & simple to -backport to stable kernels. - -Reported-by: Andy Lutomirski <luto@kernel.org> -Signed-off-by: Paul Burton <paul.burton@mips.com> -Fixes: 432c6bacbd0c ("MIPS: Use per-mm page to execute branch delay slot instructions") -Cc: stable@vger.kernel.org # v4.8+ -Cc: linux-mips@vger.kernel.org -Cc: linux-kernel@vger.kernel.org -Cc: Rich Felker <dalias@libc.org> -Cc: David Daney <david.daney@cavium.com> ---- - arch/mips/kernel/vdso.c | 4 ++-- - arch/mips/math-emu/dsemul.c | 38 ++++++++++++++++++++------------------ - 2 files changed, 22 insertions(+), 20 deletions(-) - ---- a/arch/mips/kernel/vdso.c -+++ b/arch/mips/kernel/vdso.c -@@ -111,8 +111,8 @@ int arch_setup_additional_pages(struct l - - /* Map delay slot emulation page */ - base = mmap_region(NULL, STACK_TOP, PAGE_SIZE, -- VM_READ|VM_WRITE|VM_EXEC| -- VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, -+ VM_READ | VM_EXEC | -+ VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC, - 0); - if (IS_ERR_VALUE(base)) { - ret = base; ---- a/arch/mips/math-emu/dsemul.c -+++ b/arch/mips/math-emu/dsemul.c -@@ -211,8 +211,9 @@ int mips_dsemul(struct pt_regs *regs, mi - { - int isa16 = get_isa16_mode(regs->cp0_epc); - mips_instruction break_math; -- struct emuframe __user *fr; -- int err, fr_idx; -+ unsigned long fr_uaddr; -+ struct emuframe fr; -+ int fr_idx, ret; - - /* NOP is easy */ - if (ir == 0) -@@ -247,27 +248,31 @@ int mips_dsemul(struct pt_regs *regs, mi - fr_idx = alloc_emuframe(); - if (fr_idx == BD_EMUFRAME_NONE) - return SIGBUS; -- fr = &dsemul_page()[fr_idx]; - - /* Retrieve the appropriately encoded break instruction */ - break_math = BREAK_MATH(isa16); - - /* Write the instructions to the frame */ - if (isa16) { -- err = __put_user(ir >> 16, -- (u16 __user *)(&fr->emul)); -- err |= __put_user(ir & 0xffff, -- (u16 __user *)((long)(&fr->emul) + 2)); -- err |= __put_user(break_math >> 16, -- (u16 __user *)(&fr->badinst)); -- err |= __put_user(break_math & 0xffff, -- (u16 __user *)((long)(&fr->badinst) + 2)); -+ union mips_instruction _emul = { -+ .halfword = { ir >> 16, ir } -+ }; -+ union mips_instruction _badinst = { -+ .halfword = { break_math >> 16, break_math } -+ }; -+ -+ fr.emul = _emul.word; -+ fr.badinst = _badinst.word; - } else { -- err = __put_user(ir, &fr->emul); -- err |= __put_user(break_math, &fr->badinst); -+ fr.emul = ir; -+ fr.badinst = break_math; - } - -- if (unlikely(err)) { -+ /* Write the frame to user memory */ -+ fr_uaddr = (unsigned long)&dsemul_page()[fr_idx]; -+ ret = access_process_vm(current, fr_uaddr, &fr, sizeof(fr), -+ FOLL_FORCE | FOLL_WRITE); -+ if (unlikely(ret != sizeof(fr))) { - MIPS_FPU_EMU_INC_STATS(errors); - free_emuframe(fr_idx, current->mm); - return SIGBUS; -@@ -279,10 +284,7 @@ int mips_dsemul(struct pt_regs *regs, mi - atomic_set(¤t->thread.bd_emu_frame, fr_idx); - - /* Change user register context to execute the frame */ -- regs->cp0_epc = (unsigned long)&fr->emul | isa16; -- -- /* Ensure the icache observes our newly written frame */ -- flush_cache_sigtramp((unsigned long)&fr->emul); -+ regs->cp0_epc = fr_uaddr | isa16; - - return 0; - } |