From: Kees Cook Date: Fri, 18 Aug 2017 22:16:31 +0000 (-0700) Subject: mm: revert x86_64 and arm64 ELF_ET_DYN_BASE base changes X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=240628085effc47e86f51fc3fb37bc0e628f9a85;p=GitHub%2Fexynos8895%2Fandroid_kernel_samsung_universal8895.git mm: revert x86_64 and arm64 ELF_ET_DYN_BASE base changes commit c715b72c1ba406f133217b509044c38d8e714a37 upstream. Moving the x86_64 and arm64 PIE base from 0x555555554000 to 0x000100000000 broke AddressSanitizer. This is a partial revert of: eab09532d400 ("binfmt_elf: use ELF_ET_DYN_BASE only for PIE") 02445990a96e ("arm64: move ELF_ET_DYN_BASE to 4GB / 4MB") The AddressSanitizer tool has hard-coded expectations about where executable mappings are loaded. The motivation for changing the PIE base in the above commits was to avoid the Stack-Clash CVEs that allowed executable mappings to get too close to heap and stack. This was mainly a problem on 32-bit, but the 64-bit bases were moved too, in an effort to proactively protect those systems (proofs of concept do exist that show 64-bit collisions, but other recent changes to fix stack accounting and setuid behaviors will minimize the impact). The new 32-bit PIE base is fine for ASan (since it matches the ET_EXEC base), so only the 64-bit PIE base needs to be reverted to let x86 and arm64 ASan binaries run again. Future changes to the 64-bit PIE base on these architectures can be made optional once a more dynamic method for dealing with AddressSanitizer is found. (e.g. always loading PIE into the mmap region for marked binaries.) Link: http://lkml.kernel.org/r/20170807201542.GA21271@beast Fixes: eab09532d400 ("binfmt_elf: use ELF_ET_DYN_BASE only for PIE") Fixes: 02445990a96e ("arm64: move ELF_ET_DYN_BASE to 4GB / 4MB") Signed-off-by: Kees Cook Reported-by: Kostya Serebryany Acked-by: Will Deacon Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: Thomas Gleixner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h index 9e11dbe1cec3..329c127e13dc 100644 --- a/arch/arm64/include/asm/elf.h +++ b/arch/arm64/include/asm/elf.h @@ -121,10 +121,10 @@ typedef struct user_fpsimd_state elf_fpregset_t; /* * This is the base location for PIE (ET_DYN with INTERP) loads. On - * 64-bit, this is raised to 4GB to leave the entire 32-bit address + * 64-bit, this is above 4GB to leave the entire 32-bit address * space open for things that want to use the area for 32-bit pointers. */ -#define ELF_ET_DYN_BASE 0x100000000UL +#define ELF_ET_DYN_BASE (2 * TASK_SIZE_64 / 3) /* * When the program starts, a1 contains a pointer to a function to be diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h index 07cf288b692e..bcd3d6199464 100644 --- a/arch/x86/include/asm/elf.h +++ b/arch/x86/include/asm/elf.h @@ -247,11 +247,11 @@ extern int force_personality32; /* * This is the base location for PIE (ET_DYN with INTERP) loads. On - * 64-bit, this is raised to 4GB to leave the entire 32-bit address + * 64-bit, this is above 4GB to leave the entire 32-bit address * space open for things that want to use the area for 32-bit pointers. */ #define ELF_ET_DYN_BASE (mmap_is_ia32() ? 0x000400000UL : \ - 0x100000000UL) + (TASK_SIZE / 3 * 2)) /* This yields a mask that user programs can use to figure out what instruction set this CPU supports. This could be done in user space,