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Tvrtko Ursulin 5801e65206 drm/sched: Fix potential double free in drm_sched_job_add_resv_dependencies 
When adding dependencies with drm_sched_job_add_dependency(), that
function consumes the fence reference both on success and failure, so in
the latter case the dma_fence_put() on the error path (xarray failed to
expand) is a double free.

Interestingly this bug appears to have been present ever since
commit ebd5f74255 ("drm/sched: Add dependency tracking"), since the code
back then looked like this:

drm_sched_job_add_implicit_dependencies():
...
       for (i = 0; i < fence_count; i++) {
               ret = drm_sched_job_add_dependency(job, fences[i]);
               if (ret)
                       break;
       }

       for (; i < fence_count; i++)
               dma_fence_put(fences[i]);

Which means for the failing 'i' the dma_fence_put was already a double
free. Possibly there were no users at that time, or the test cases were
insufficient to hit it.

The bug was then only noticed and fixed after
commit 9c2ba26535 ("drm/scheduler: use new iterator in drm_sched_job_add_implicit_dependencies v2")
landed, with its fixup of
commit 4eaf02d607 ("drm/scheduler: fix drm_sched_job_add_implicit_dependencies").

At that point it was a slightly different flavour of a double free, which
commit 963d0b3569 ("drm/scheduler: fix drm_sched_job_add_implicit_dependencies harder")
noticed and attempted to fix.

But it only moved the double free from happening inside the
drm_sched_job_add_dependency(), when releasing the reference not yet
obtained, to the caller, when releasing the reference already released by
the former in the failure case.

As such it is not easy to identify the right target for the fixes tag so
lets keep it simple and just continue the chain.

While fixing we also improve the comment and explain the reason for taking
the reference and not dropping it.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Fixes: 963d0b3569 ("drm/scheduler: fix drm_sched_job_add_implicit_dependencies harder")
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/dri-devel/aNFbXq8OeYl3QSdm@stanley.mountain/
Cc: Christian König <christian.koenig@amd.com>
Cc: Rob Clark <robdclark@chromium.org>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Philipp Stanner <phasta@kernel.org>
Cc: Christian König <ckoenig.leichtzumerken@gmail.com>
Cc: dri-devel@lists.freedesktop.org
Cc: stable@vger.kernel.org # v5.16+
Signed-off-by: Philipp Stanner <phasta@kernel.org>
Link: https://lore.kernel.org/r/20251015084015.6273-1-tvrtko.ursulin@igalia.com
2025-10-16 14:26:05 +02:00
arch Kbuild fixes for 6.18 #1 2025-10-11 15:47:12 -07:00
block block-6.18-20251009 2025-10-10 10:37:13 -07:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto This push contains the following changes: 2025-10-10 08:56:16 -07:00
Documentation RTC for 6.18 2025-10-11 11:56:47 -07:00
drivers drm/sched: Fix potential double free in drm_sched_job_add_resv_dependencies 2025-10-16 14:26:05 +02:00
fs - Avoid -Wflex-array-member-not-at-end warnings 2025-10-10 14:06:02 -07:00
include drm/gpuvm: Fix kernel-doc warning for drm_gpuvm_map_req.map 2025-10-15 18:37:05 +02:00
init printk changes for 6.18 2025-10-04 11:13:11 -07:00
io_uring io_uring/zcrx: increment fallback loop src offset 2025-10-08 07:26:14 -06:00
ipc namespace-6.18-rc1 2025-09-29 11:20:29 -07:00
kernel tracing fixes for v6.18: 2025-10-11 16:06:04 -07:00
lib lib/test_kho: use kho_preserve_vmalloc instead of storing addresses in fdt 2025-10-07 13:48:56 -07:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm slab hotfix for 6.18-rc1 2025-10-11 10:40:24 -07:00
net bpf-fixes 2025-10-11 10:31:38 -07:00
rust 7 hotfixes. All 7 are cc:stable and all 7 are for MM. 2025-10-11 10:14:55 -07:00
samples Char/Misc/IIO/Binder changes for 6.18-rc1 2025-10-04 16:26:32 -07:00
scripts Kbuild fixes for 6.18 #1 2025-10-11 15:47:12 -07:00
security integrity-v6.18 2025-10-05 10:48:33 -07:00
sound sound fixes for 6.18-rc1 2025-10-10 09:55:19 -07:00
tools - Remove a bunch of asm implementing condition flags testing in KVM's 2025-10-11 11:19:16 -07:00
usr gen_init_cpio: Ignore fsync() returning EINVAL on pipes 2025-10-07 09:53:05 -07:00
virt hyperv-next for v6.18 2025-10-07 08:40:15 -07:00
.clang-format memblock: drop for_each_free_mem_pfn_range_in_zone_from() 2025-09-14 08:49:03 +03:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore .gitignore: ignore compile_commands.json globally 2025-08-12 15:53:55 -07:00
.mailmap MAINTAINERS, .mailmap: update Umang's email address 2025-10-07 13:48:55 -07:00
.pylintrc tools: docs: parse-headers.py: move it from sphinx dir 2025-08-29 15:54:42 -06:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING
CREDITS USB/Thunderbolt changes for 6.18-rc1 2025-10-04 16:07:08 -07:00
Kbuild sched: Make migrate_{en,dis}able() inline 2025-09-25 09:57:16 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS Just one series here - Mike Rappoport has taught KEXEC handover to 2025-10-11 10:27:52 -07:00
Makefile Linux 6.18-rc1 2025-10-12 13:42:36 -07:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

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 reStructuredText 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.