arm64: introduce separated bits for mm_context_t flags

Currently mm->context.flags field uses thread_info flags which is not
the best idea for many reasons. For example, mm_context_t doesn't need
most of thread_info flags. And it would be difficult to add new mm-related
flag if needed because it may easily interfere with TIF ones.

To deal with it, the new MMCF_AARCH32 flag is introduced for
mm_context_t->flags, where MMCF prefix stands for mm_context_t flags.
Also, mm_context_t flag doesn't require atomicity and ordering of the
access, so using set/clear_bit() is replaced with simple masks.

Signed-off-by: Yury Norov <ynorov@caviumnetworks.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
(cherry picked from commit 5ce93ab624cee4ed68086c946bd6d18b9b3f64aa)

CVE-2017-5753
CVE-2017-5715
CVE-2017-5754

Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>
Acked-by: Brad Figg <brad.figg@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
index 3288c2b3673149b728ea52ee87bc65ba723c9811..517b9ff0456cae47ae71346e35650579bcd52c39 100644 (file)
--- a/arch/arm64/include/asm/elf.h
+++ b/arch/arm64/include/asm/elf.h
@@ -139,7 +139,7 @@ typedef struct user_fpsimd_state elf_fpregset_t;
 
 #define SET_PERSONALITY(ex)                                            \
 ({                                                                     \
-       clear_bit(TIF_32BIT, &current->mm->context.flags);              \
+       current->mm->context.flags = 0;                                 \
        clear_thread_flag(TIF_32BIT);                                   \
        current->personality &= ~READ_IMPLIES_EXEC;                     \
 })
@@ -195,7 +195,7 @@ typedef compat_elf_greg_t           compat_elf_gregset_t[COMPAT_ELF_NGREG];
  */
 #define COMPAT_SET_PERSONALITY(ex)                                     \
 ({                                                                     \
-       set_bit(TIF_32BIT, &current->mm->context.flags);                \
+       current->mm->context.flags = MMCF_AARCH32;                      \
        set_thread_flag(TIF_32BIT);                                     \
  })
 #define COMPAT_ARCH_DLINFO

diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index 5468c834b072b2a29701a69e0468b0b32cafba4d..0d34bf0a89c7241bdd89a7a6a4634f7a4af31dd5 100644 (file)
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -16,6 +16,8 @@
 #ifndef __ASM_MMU_H
 #define __ASM_MMU_H
 
+#define MMCF_AARCH32   0x1     /* mm context flag for AArch32 executables */
+
 typedef struct {
        atomic64_t      id;
        void            *vdso;

diff --git a/arch/arm64/kernel/probes/uprobes.c b/arch/arm64/kernel/probes/uprobes.c
index 26c998534dca9a545d006ba5a637a7c1dd24aa52..636ca0119c0efa7cb1254568d04edfdddf791db9 100644 (file)
--- a/arch/arm64/kernel/probes/uprobes.c
+++ b/arch/arm64/kernel/probes/uprobes.c
@@ -40,7 +40,7 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
        probe_opcode_t insn;
 
        /* TODO: Currently we do not support AARCH32 instruction probing */
-       if (test_bit(TIF_32BIT, &mm->context.flags))
+       if (mm->context.flags & MMCF_AARCH32)
                return -ENOTSUPP;
        else if (!IS_ALIGNED(addr, AARCH64_INSN_SIZE))
                return -EINVAL;