On Sun, Mar 12, 2023 at 04:56:23PM -0300, Alexandre Oliva wrote:
If two or more suitable entries with the same filename are found in __uc_fw_auto_select's fw_blobs, and that filename fails to load in the first attempt and in the retry, when __uc_fw_auto_select is called for the third time, the coincidence of strings will cause it to clear file_selected.path at the first hit, so it will return the second hit over and over again, indefinitely.
Of course this doesn't occur with the pristine blob lists, but a modified version could run into this, e.g., patching in a duplicate entry, or (as in our case) disarming blob loading by remapping their names to "/*(DEBLOBBED)*/", given a toolchain that unifies identical string literals.
Of course I'm ready to carry a patchlet to avoid this problem triggered by our (GNU Linux-libre's) intentional changes, but I figured you might be interested in fail-safing it even in accidental backporting circumstances. I realize it's not entirely foolproof: if the same string appears in two entries separated by a different one, the infinite loop might still occur. Catching that even more unlikely situation seemed too expensive.
Link: https://www.fsfla.org/pipermail/linux-libre/2023-March/003506.html Cc: intel-gfx@lists.freedesktop.org Cc: stable@vger.kernel.org # 6.[12].x Signed-off-by: Alexandre Oliva lxoliva@fsfla.org
Cc: Daniele Ceraolo Spurio daniele.ceraolospurio@intel.com Cc: John Harrison John.C.Harrison@Intel.com
drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c b/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c index 9d6f571097e6..2b7564a3ed82 100644 --- a/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c +++ b/drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c @@ -259,7 +259,10 @@ __uc_fw_auto_select(struct drm_i915_private *i915, struct intel_uc_fw *uc_fw)
Since __uc_fw_auto_select is also called from another place, intel_uc_fw_init_early out of the intel_uc_fw_fetch infinite loop, I'm afraid this proposal below could have some side-effect.
I hope Daniele and John have a better understanding and can provide some guidance or acks here.
uc_fw->file_selected.path = NULL;continue;
}
} else if (uc_fw->file_wanted.path == blob->path)/* Avoid retrying forever when neighborentries point to the same path. */continue;uc_fw->file_selected.path = blob->path; uc_fw->file_wanted.path = blob->path; -- 2.25.1
-- Alexandre Oliva, happy hacker https://FSFLA.org/blogs/lxo/ Free Software Activist GNU Toolchain Engineer Disinformation flourishes because many people care deeply about injustice but very few check the facts. Ask me about https://stallmansupport.org