diff options
| author | Dave Hansen <dave.hansen@linux.intel.com> | 2015-11-11 19:19:34 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-11-12 09:20:37 +0100 |
| commit | f3119b830264d89d216bfb378ab65065dffa02d9 (patch) | |
| tree | 7f2be5200427719335b0549c319ecc73728c61af /arch/x86 | |
| parent | x86/mpx: Do proper get_user() when running 32-bit binaries on 64-bit kernels (diff) | |
| download | linux-f3119b830264d89d216bfb378ab65065dffa02d9.tar.xz linux-f3119b830264d89d216bfb378ab65065dffa02d9.zip | |
x86/mpx: Fix 32-bit address space calculation
I received a bug report that running 32-bit MPX binaries on
64-bit kernels was broken. I traced it down to this little code
snippet. We were switching our "number of bounds directory
entries" calculation correctly. But, we didn't switch the other
side of the calculation: the virtual space size.
This meant that we were calculating an absurd size for
bd_entry_virt_space() on 32-bit because we used the 64-bit
virt_space.
This was _also_ broken for 32-bit kernels running on 64-bit
hardware since boot_cpu_data.x86_virt_bits=48 even when running
in 32-bit mode.
Correct that and properly handle all 3 possible cases:
1. 32-bit binary on 64-bit kernel
2. 64-bit binary on 64-bit kernel
3. 32-bit binary on 32-bit kernel
This manifested in having bounds tables not properly unmapped.
It "leaked" memory but had no functional impact otherwise.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: <stable@vger.kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20151111181934.FA7FAC34@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/mm/mpx.c | 22 |
1 files changed, 17 insertions, 5 deletions
diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c index 6127c5e3a19b..1202d5ca2fb5 100644 --- a/arch/x86/mm/mpx.c +++ b/arch/x86/mm/mpx.c @@ -723,11 +723,23 @@ static unsigned long mpx_get_bt_entry_offset_bytes(struct mm_struct *mm, */ static inline unsigned long bd_entry_virt_space(struct mm_struct *mm) { - unsigned long long virt_space = (1ULL << boot_cpu_data.x86_virt_bits); - if (is_64bit_mm(mm)) - return virt_space / MPX_BD_NR_ENTRIES_64; - else - return virt_space / MPX_BD_NR_ENTRIES_32; + unsigned long long virt_space; + unsigned long long GB = (1ULL << 30); + + /* + * This covers 32-bit emulation as well as 32-bit kernels + * running on 64-bit harware. + */ + if (!is_64bit_mm(mm)) + return (4ULL * GB) / MPX_BD_NR_ENTRIES_32; + + /* + * 'x86_virt_bits' returns what the hardware is capable + * of, and returns the full >32-bit adddress space when + * running 32-bit kernels on 64-bit hardware. + */ + virt_space = (1ULL << boot_cpu_data.x86_virt_bits); + return virt_space / MPX_BD_NR_ENTRIES_64; } /* |