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@xxxxxxxxxxxxxxxxxxxxx > Cc: stable@xxxxxxxxxxxxxxx # 6.[12].x > Signed-off-by: Alexandre Oliva <lxoliva@xxxxxxxxx> Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@xxxxxxxxx> Cc: John Harrison <John.C.Harrison@xxxxxxxxx> > --- > 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 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>
