d231c15aff
Inside print_request(), we query the context/timeline name. Nothing immediately protects the context from being freed if the request is complete -- we rely on serialisation by the caller to keep the name valid until they finish using it. Inside intel_engine_dump(), we generally only print the requests in the execution queue protected by the engine->active.lock, but we also show the pending execlists ports which are not protected and so require a rcu_read_lock to keep the pointer valid. [ 1695.700883] BUG: KASAN: use-after-free in i915_fence_get_timeline_name+0x53/0x90 [i915] [ 1695.700981] Read of size 8 at addr ffff8887344f4d50 by task gem_ctx_persist/2968 [ 1695.701068] [ 1695.701156] CPU: 1 PID: 2968 Comm: gem_ctx_persist Tainted: G U 5.4.0-rc6+ #331 [ 1695.701246] Hardware name: Intel Corporation NUC7i5BNK/NUC7i5BNB, BIOS BNKBL357.86A.0052.2017.0918.1346 09/18/2017 [ 1695.701334] Call Trace: [ 1695.701424] dump_stack+0x5b/0x90 [ 1695.701870] ? i915_fence_get_timeline_name+0x53/0x90 [i915] [ 1695.701964] print_address_description.constprop.7+0x36/0x50 [ 1695.702408] ? i915_fence_get_timeline_name+0x53/0x90 [i915] [ 1695.702856] ? i915_fence_get_timeline_name+0x53/0x90 [i915] [ 1695.702947] __kasan_report.cold.10+0x1a/0x3a [ 1695.703390] ? i915_fence_get_timeline_name+0x53/0x90 [i915] [ 1695.703836] i915_fence_get_timeline_name+0x53/0x90 [i915] [ 1695.704241] print_request+0x82/0x2e0 [i915] [ 1695.704638] ? fwtable_read32+0x133/0x360 [i915] [ 1695.705042] ? write_timestamp+0x110/0x110 [i915] [ 1695.705133] ? _raw_spin_lock_irqsave+0x79/0xc0 [ 1695.705221] ? refcount_inc_not_zero_checked+0x91/0x110 [ 1695.705306] ? refcount_dec_and_mutex_lock+0x50/0x50 [ 1695.705709] ? intel_engine_find_active_request+0x202/0x230 [i915] [ 1695.706115] intel_engine_dump+0x2c9/0x900 [i915] Fixes: c36eebd9ba5d ("drm/i915/gt: execlists->active is serialised by the tasklet") Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20191111114323.5833-1-chris@chris-wilson.co.uk (cherry picked from commit fecffa4668cf62e679aeea8caa9d0f241f822578) Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.