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(a)lists.freedesktop.org
Cc: stable(a)vger.kernel.org # 6.[12].x
Signed-off-by: Alexandre Oliva <lxoliva(a)fsfla.org>
---
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)
uc_fw->file_selected.path = NULL;
continue;
- }
+ } else if (uc_fw->file_wanted.path == blob->path)
+ /* Avoid retrying forever when neighbor
+ entries 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>