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? Other than that, Reviewed-by: SeongJae Park <sjpark@xxxxxxxxx> Thanks, SeongJae Park
