The quilt patch titled
Subject: lib/stackdepot: annotate racy pool_index accesses
has been removed from the -mm tree. Its filename was
lib-stackdepot-annotate-racy-pool_index-accesses.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Subject: lib/stackdepot: annotate racy pool_index accesses
Date: Fri, 10 Feb 2023 22:16:04 +0100
Accesses to pool_index are protected by pool_lock everywhere except
in a sanity check in stack_depot_fetch. The read access there can race
with the write access in depot_alloc_stack.
Use WRITE/READ_ONCE() to annotate the racy accesses.
As the sanity check is only used to print a warning in case of a
violation of the stack depot interface usage, it does not make a lot
of sense to use proper synchronization.
[andreyknvl@xxxxxxxxxx: s/pool_index/pool_index_cached/ in stack_depot_fetch()]
Link: https://lkml.kernel.org/r/95cf53f0da2c112aa2cc54456cbcd6975c3ff343.1676129911.git.andreyknvl@xxxxxxxxxx
Link: https://lkml.kernel.org/r/359ac9c13cd0869c56740fb2029f505e41593830.1676063693.git.andreyknvl@xxxxxxxxxx
Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Reviewed-by: Alexander Potapenko <glider@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/lib/stackdepot.c~lib-stackdepot-annotate-racy-pool_index-accesses
+++ a/lib/stackdepot.c
@@ -278,8 +278,12 @@ depot_alloc_stack(unsigned long *entries
return NULL;
}
- /* Move on to the next pool. */
- pool_index++;
+ /*
+ * Move on to the next pool.
+ * WRITE_ONCE pairs with potential concurrent read in
+ * stack_depot_fetch().
+ */
+ WRITE_ONCE(pool_index, pool_index + 1);
pool_offset = 0;
/*
* If the maximum number of pools is not reached, take note
@@ -502,6 +506,11 @@ unsigned int stack_depot_fetch(depot_sta
unsigned long **entries)
{
union handle_parts parts = { .handle = handle };
+ /*
+ * READ_ONCE pairs with potential concurrent write in
+ * depot_alloc_stack.
+ */
+ int pool_index_cached = READ_ONCE(pool_index);
void *pool;
size_t offset = parts.offset << DEPOT_STACK_ALIGN;
struct stack_record *stack;
@@ -510,9 +519,9 @@ unsigned int stack_depot_fetch(depot_sta
if (!handle)
return 0;
- if (parts.pool_index > pool_index) {
+ if (parts.pool_index > pool_index_cached) {
WARN(1, "pool index %d out of bounds (%d) for stack id %08x\n",
- parts.pool_index, pool_index, handle);
+ parts.pool_index, pool_index_cached, handle);
return 0;
}
pool = stack_pools[parts.pool_index];
_
Patches currently in -mm which might be from andreyknvl@xxxxxxxxxx are
