On Fri, 25 Sep 2020 at 13:24, 'SeongJae Park' via kasan-dev <kasan-dev@xxxxxxxxxxxxxxxx> wrote: > > On Mon, 21 Sep 2020 15:26:02 +0200 Marco Elver <elver@xxxxxxxxxx> wrote: > > > From: Alexander Potapenko <glider@xxxxxxxxxx> > > > > This adds the Kernel Electric-Fence (KFENCE) infrastructure. KFENCE is a > > low-overhead sampling-based memory safety error detector of heap > > use-after-free, invalid-free, and out-of-bounds access errors. > > > > KFENCE is designed to be enabled in production kernels, and has near > > zero performance overhead. Compared to KASAN, KFENCE trades performance > > for precision. The main motivation behind KFENCE's design, is that with > > enough total uptime KFENCE will detect bugs in code paths not typically > > exercised by non-production test workloads. One way to quickly achieve a > > large enough total uptime is when the tool is deployed across a large > > fleet of machines. > > > > KFENCE objects each reside on a dedicated page, at either the left or > > right page boundaries. The pages to the left and right of the object > > page are "guard pages", whose attributes are changed to a protected > > state, and cause page faults on any attempted access to them. Such page > > faults are then intercepted by KFENCE, which handles the fault > > gracefully by reporting a memory access error. To detect out-of-bounds > > writes to memory within the object's page itself, KFENCE also uses > > pattern-based redzones. The following figure illustrates the page > > layout: > > > > ---+-----------+-----------+-----------+-----------+-----------+--- > > | xxxxxxxxx | O : | xxxxxxxxx | : O | xxxxxxxxx | > > | xxxxxxxxx | B : | xxxxxxxxx | : B | xxxxxxxxx | > > | x GUARD x | J : RED- | x GUARD x | RED- : J | x GUARD x | > > | xxxxxxxxx | E : ZONE | xxxxxxxxx | ZONE : E | xxxxxxxxx | > > | xxxxxxxxx | C : | xxxxxxxxx | : C | xxxxxxxxx | > > | xxxxxxxxx | T : | xxxxxxxxx | : T | xxxxxxxxx | > > ---+-----------+-----------+-----------+-----------+-----------+--- > > > > Guarded allocations are set up based on a sample interval (can be set > > via kfence.sample_interval). After expiration of the sample interval, a > > guarded allocation from the KFENCE object pool is returned to the main > > allocator (SLAB or SLUB). At this point, the timer is reset, and the > > next allocation is set up after the expiration of the interval. > > > > To enable/disable a KFENCE allocation through the main allocator's > > fast-path without overhead, KFENCE relies on static branches via the > > static keys infrastructure. The static branch is toggled to redirect the > > allocation to KFENCE. To date, we have verified by running synthetic > > benchmarks (sysbench I/O workloads) that a kernel compiled with KFENCE > > is performance-neutral compared to the non-KFENCE baseline. > > > > For more details, see Documentation/dev-tools/kfence.rst (added later in > > the series). > > > > Reviewed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> > > Co-developed-by: Marco Elver <elver@xxxxxxxxxx> > > Signed-off-by: Marco Elver <elver@xxxxxxxxxx> > > Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx> > > --- > > v3: > > * Reports by SeongJae Park: > > * Remove reference to Documentation/dev-tools/kfence.rst. > > * Remove redundant braces. > > * Use CONFIG_KFENCE_NUM_OBJECTS instead of ARRAY_SIZE(...). > > * Align some comments. > > * Add figure from Documentation/dev-tools/kfence.rst added later in > > series to patch description. > > > > v2: > > * Add missing __printf attribute to seq_con_printf, and fix new warning. > > [reported by kernel test robot <lkp@xxxxxxxxx>] > > * Fix up some comments [reported by Jonathan Cameron]. > > * Remove 2 cases of redundant stack variable initialization > > [reported by Jonathan Cameron]. > > * Fix printf format [reported by kernel test robot <lkp@xxxxxxxxx>]. > > * Print (in kfence-#nn) after address, to more clearly establish link > > between first and second stacktrace [reported by Andrey Konovalov]. > > * Make choice between KASAN and KFENCE clearer in Kconfig help text > > [suggested by Dave Hansen]. > > * Document CONFIG_KFENCE_SAMPLE_INTERVAL=0. > > * Shorten memory corruption report line length. > > * Make /sys/module/kfence/parameters/sample_interval root-writable for > > all builds (to enable debugging, automatic dynamic tweaking). > > * Reports by Dmitry Vyukov: > > * Do not store negative size for right-located objects > > * Only cache-align addresses of right-located objects. > > * Run toggle_allocation_gate() after KFENCE is enabled. > > * Add empty line between allocation and free stacks. > > * Add comment about SLAB_TYPESAFE_BY_RCU. > > * Also skip internals for allocation/free stacks. > > * s/KFENCE_FAULT_INJECTION/KFENCE_STRESS_TEST_FAULTS/ as FAULT_INJECTION > > is already overloaded in different contexts. > > * Parenthesis for macro variable. > > * Lower max of KFENCE_NUM_OBJECTS config variable. > > --- > > MAINTAINERS | 11 + > > include/linux/kfence.h | 174 ++++++++++ > > init/main.c | 2 + > > lib/Kconfig.debug | 1 + > > lib/Kconfig.kfence | 63 ++++ > > mm/Makefile | 1 + > > mm/kfence/Makefile | 3 + > > mm/kfence/core.c | 733 +++++++++++++++++++++++++++++++++++++++++ > > mm/kfence/kfence.h | 102 ++++++ > > mm/kfence/report.c | 219 ++++++++++++ > > 10 files changed, 1309 insertions(+) > > create mode 100644 include/linux/kfence.h > > create mode 100644 lib/Kconfig.kfence > > create mode 100644 mm/kfence/Makefile > > create mode 100644 mm/kfence/core.c > > create mode 100644 mm/kfence/kfence.h > > create mode 100644 mm/kfence/report.c > > > > diff --git a/MAINTAINERS b/MAINTAINERS > > index b5cfab015bd6..863899ed9a29 100644 > > --- a/MAINTAINERS > > +++ b/MAINTAINERS > > @@ -9673,6 +9673,17 @@ F: include/linux/keyctl.h > > F: include/uapi/linux/keyctl.h > > F: security/keys/ > > > > +KFENCE > > +M: Alexander Potapenko <glider@xxxxxxxxxx> > > +M: Marco Elver <elver@xxxxxxxxxx> > > +R: Dmitry Vyukov <dvyukov@xxxxxxxxxx> > > +L: kasan-dev@xxxxxxxxxxxxxxxx > > +S: Maintained > > +F: Documentation/dev-tools/kfence.rst > > This patch doesn't introduce this file yet, right? How about using a separate > final patch for MAINTAINERS update? Sure. > Other than that, > > Reviewed-by: SeongJae Park <sjpark@xxxxxxxxx> Thanks!
