This is a note to let you know that I've just added the patch titled
dyndbg: fix static_branch manipulation
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
dyndbg-fix-static_branch-manipulation.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 098b2ea3fdc77d8c2fe455eea437839340aa3f78
Author: Jim Cromie <jim.cromie@xxxxxxxxx>
Date: Sun Sep 4 15:40:38 2022 -0600
dyndbg: fix static_branch manipulation
[ Upstream commit ee879be38bc87f8cedc79ae2742958db6533ca59 ]
In https://lore.kernel.org/lkml/20211209150910.GA23668@xxxxxxxx/
Vincent's patch commented on, and worked around, a bug toggling
static_branch's, when a 2nd PRINTK-ish flag was added. The bug
results in a premature static_branch_disable when the 1st of 2 flags
was disabled.
The cited commit computed newflags, but then in the JUMP_LABEL block,
failed to use that result, instead using just one of the terms in it.
Using newflags instead made the code work properly.
This is Vincents test-case, reduced. It needs the 2nd flag to
demonstrate the bug, but it's explanatory here.
pt_test() {
echo 5 > /sys/module/dynamic_debug/verbose
site="module tcp" # just one callsite
echo " $site =_ " > /proc/dynamic_debug/control # clear it
# A B ~A ~B
for flg in +T +p "-T #broke here" -p; do
echo " $site $flg " > /proc/dynamic_debug/control
done;
# A B ~B ~A
for flg in +T +p "-p #broke here" -T; do
echo " $site $flg " > /proc/dynamic_debug/control
done
}
pt_test
Fixes: 84da83a6ffc0 dyndbg: combine flags & mask into a struct, simplify with it
CC: vincent.whitchurch@xxxxxxxx
Acked-by: Jason Baron <jbaron@xxxxxxxxxx>
Acked-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Signed-off-by: Jim Cromie <jim.cromie@xxxxxxxxx>
Link: https://lore.kernel.org/r/20220904214134.408619-2-jim.cromie@xxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 84c16309cc63..00e6507972d8 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -207,10 +207,11 @@ static int ddebug_change(const struct ddebug_query *query,
continue;
#ifdef CONFIG_JUMP_LABEL
if (dp->flags & _DPRINTK_FLAGS_PRINT) {
- if (!(modifiers->flags & _DPRINTK_FLAGS_PRINT))
+ if (!(newflags & _DPRINTK_FLAGS_PRINT))
static_branch_disable(&dp->key.dd_key_true);
- } else if (modifiers->flags & _DPRINTK_FLAGS_PRINT)
+ } else if (newflags & _DPRINTK_FLAGS_PRINT) {
static_branch_enable(&dp->key.dd_key_true);
+ }
#endif
dp->flags = newflags;
v2pr_info("changed %s:%d [%s]%s =%s\n",
