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| author | dcashman <dcashman@google.com> | 2015-10-02 12:52:57 -0700 |
|---|---|---|
| committer | Mark Salyzyn <salyzyn@google.com> | 2015-10-28 14:31:17 +0000 |
| commit | 565ef50330f97868b8d01b78c7809e453679ba76 (patch) | |
| tree | d2ae195b5e03750ba685a8430f86e0fcdc1f3bbd | |
| parent | 70f767ae180a8b7ab0058145ed5375bc357a39a6 (diff) | |
| download | linux-linaro-stable-565ef50330f97868b8d01b78c7809e453679ba76.tar.gz | |
mm: mmap: Add new /proc tunable for mmap_base ASLR.
ASLR currently only uses 8 bits to generate the random offset for the
mmap base address on 32 bit architectures. This value was chosen to
prevent a poorly chosen value from dividing the address space in such
a way as to prevent large allocations. This may not be an issue on all
platforms. Allow the specification of a minimum number of bits so that
platforms desiring greater ASLR protection may determine where to place
the trade-off.
BUG=24047224
Signed-off-by: Daniel Cashman <dcashman@google.com>
Change-Id: I0aa8f1e416fec848b6817ab861610d8f0eb3beb8
| -rw-r--r-- | Documentation/sysctl/kernel.txt | 14 | ||||
| -rw-r--r-- | include/linux/mm.h | 6 | ||||
| -rw-r--r-- | kernel/sysctl.c | 11 |
3 files changed, 31 insertions, 0 deletions
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt index 57baff5bdb80..62044945a118 100644 --- a/Documentation/sysctl/kernel.txt +++ b/Documentation/sysctl/kernel.txt @@ -41,6 +41,7 @@ show up in /proc/sys/kernel: - kptr_restrict - kstack_depth_to_print [ X86 only ] - l2cr [ PPC only ] +- mmap_rnd_bits - modprobe ==> Documentation/debugging-modules.txt - modules_disabled - msg_next_id [ sysv ipc ] @@ -386,6 +387,19 @@ This flag controls the L2 cache of G3 processor boards. If ============================================================== +mmap_rnd_bits: + +This value can be used to select the number of bits to use to +determine the random offset to the base address of vma regions +resulting from mmap allocations on architectures which support +tuning address space randomization. This value will be bounded +by the architecture's minimum and maximum supported values. + +This value can be changed after boot using the +/proc/sys/kernel/mmap_rnd_bits tunable + +============================================================== + modules_disabled: A toggle value indicating if modules are allowed to be loaded diff --git a/include/linux/mm.h b/include/linux/mm.h index 18a4997dcde7..1fb49a650c17 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -48,6 +48,12 @@ extern int sysctl_legacy_va_layout; #define sysctl_legacy_va_layout 0 #endif +#ifdef CONFIG_ARCH_MMAP_RND_BITS +extern int mmap_rnd_bits_min; +extern int mmap_rnd_bits_max; +extern int mmap_rnd_bits; +#endif + #include <asm/page.h> #include <asm/pgtable.h> #include <asm/processor.h> diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 78af9692e0a4..a6de89ef2191 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -1106,6 +1106,17 @@ static struct ctl_table kern_table[] = { .proc_handler = proc_dointvec, }, #endif +#ifdef CONFIG_ARCH_MMAP_RND_BITS + { + .procname = "mmap_rnd_bits", + .data = &mmap_rnd_bits, + .maxlen = sizeof(mmap_rnd_bits), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = &mmap_rnd_bits_min, + .extra2 = &mmap_rnd_bits_max, + }, +#endif { } }; |