[PATCH v3 0/4] drm/nouveau: fix list cursor use after loop in the clk pstate paths

[Francesco Magazzu]

This series deals with the three places in the nouveau clk pstate code
where the list_for_each_entry() cursor is used after the loop, plus one
unrelated fix.  They are exactly the three sites Dan Carpenter listed in
2022.

The only change in v3 is the one Lyude asked for: patch 1 is Dan's
original patch again, with his authorship and his Signed-off-by
restored.  The code is unchanged from what he posted; I only expanded
the commit message and noted that below the ---.

His Signed-off-by is kept with the address he signed it with in 2022
(dan.carpenter@xxxxxxxxxx); .mailmap already maps it to the address he
uses today, and I did not want to rewrite someone else's tag.  Say the
word if you would rather have error27@xxxxxxxxx in there.  Dan is Cc'd
at that address this time - the v2 went to his old linaro.org one, which
is dead, so he most likely never saw it.

Patches 2, 3 and 4 are unchanged from v2 and carry Lyude's Reviewed-by.

Only patch 1 fixes a bug that can actually be triggered:
nvkm_clk_ustate_update() takes an arbitrary pstate id from the user and
never checks that a matching entry exists, so if it does not the cursor
ends up pointing at the list head and the code reads past it.

Patches 2 and 3 fix the same pattern in nvkm_pstate_prog() and
nvkm_control_mthd_pstate_attr(), but neither is triggerable as the code
stands: the callers of nvkm_pstate_prog() clamp the index against
clk->state_nr first, and nvkm_control_mthd_pstate_attr() already rejects
args->v0.state >= clk->state_nr before the loop.  Both are hardening, not
bug fixes, and they carry no Fixes: tag on purpose.  The point is to stop
the two functions from being correct only by virtue of what their callers
do.

Patch 4 is unrelated and is a real bug, though a modest one:
nvkm_cstate_prog() overwrites the reclock status in 'ret' with the status
of the voltage/fan restore calls it makes afterwards.  The only consumer of
the return value is an error message in nvkm_pstate_work(), so the
observable effect is that a failing reclock is never reported in dmesg.

Compile-tested only.  All the affected paths are reachable only by root,
through the 'pstate' debugfs file, so I could not exercise them in any
other way.

The two follow-up patches for nvkm_pstate_prog() that Lyude also reviewed
apply on top of this series and are not resent here:
https://lore.kernel.org/dri-devel/20260727152821.128432-1-postadelmaga@xxxxxxxxx/

v3: restore Dan Carpenter's authorship on patch 1 (Lyude), collect the
Reviewed-by tags, rebase on drm-misc-next.
Link to v2:
https://lore.kernel.org/dri-devel/20260712123616.1180830-1-postadelmaga@xxxxxxxxx/
Link to Lyude's review of patch 1:
https://lore.kernel.org/dri-devel/ad023b5df1495ced25aa681d10f57628df41ac13.camel@xxxxxxxxxx/
Link to Dan's original patch:
https://lore.kernel.org/dri-devel/YvSkKAdk8Pe0g2K9@kili/

Dan Carpenter (1):
  drm/nouveau/clk: fix list cursor use after loop in
    nvkm_clk_ustate_update

Francesco Magazzu (3):
  drm/nouveau/clk: don't use the pstate cursor after the loop
  drm/nouveau/device: don't use the pstate cursor after the loop
  drm/nouveau/clk: don't clobber reclock status when restoring volt/fan

 .../gpu/drm/nouveau/nvkm/engine/device/ctrl.c |  8 ++++-
 .../gpu/drm/nouveau/nvkm/subdev/clk/base.c    | 31 +++++++++++++------
 2 files changed, 28 insertions(+), 11 deletions(-)


base-commit: bc47d5937f21c5fc94504f03e18f1adb56d97634
-- 
2.55.0