The patch titled
Subject: lib/stackdepot: annotate racy pool_index accesses
has been added to the -mm mm-nonmm-unstable branch. Its filename is
lib-stackdepot-annotate-racy-pool_index-accesses.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/lib-stackdepot-annotate-racy-pool_index-accesses.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
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.
Link: https://lkml.kernel.org/r/359ac9c13cd0869c56740fb2029f505e41593830.1676063693.git.andreyknvl@xxxxxxxxxx
Signed-off-by: Andrey Konovalov <andreyknvl@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;
@@ -510,7 +519,7 @@ 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);
return 0;
_
Patches currently in -mm which might be from andreyknvl@xxxxxxxxxx are
lib-stackdepot-put-functions-in-logical-order.patch
lib-stackdepot-use-pr_fmt-to-define-message-format.patch
lib-stackdepot-mm-rename-stack_depot_want_early_init.patch
lib-stackdepot-rename-stack_depot_disable.patch
lib-stackdepot-annotate-init-and-early-init-functions.patch
lib-stackdepot-lower-the-indentation-in-stack_depot_init.patch
lib-stackdepot-reorder-and-annotate-global-variables.patch
lib-stackdepot-rename-hash-table-constants-and-variables.patch
lib-stackdepot-rename-slab-to-pool.patch
lib-stackdepot-rename-handle-and-pool-constants.patch
lib-stackdepot-rename-init_stack_pool.patch
lib-stacktrace-drop-impossible-warn_on-for-depot_init_pool.patch
lib-stackdepot-annotate-depot_init_pool-and-depot_alloc_stack.patch
lib-stackdepot-rename-next_pool_inited-to-next_pool_required.patch
lib-stacktrace-kasan-kmsan-rework-extra_bits-interface.patch
lib-stackdepot-annotate-racy-pool_index-accesses.patch
lib-stackdepot-various-comments-clean-ups.patch
lib-stackdepot-move-documentation-comments-to-stackdepoth.patch
