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authorAndrey Konovalov <andreyknvl@google.com>2023-02-10 22:16:04 +0100
committerAndrew Morton <akpm@linux-foundation.org>2023-02-16 20:43:51 -0800
commitbeb3c23c69a91a10f247e93ffef1fcd0209d93e4 (patch)
treeb5c3d6e4e1d38541fc1e8f298f66e6f741012134 /lib
parent36aa1e6779c3c6f8e0d4552544214f5cffe3c287 (diff)
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lib/stackdepot: annotate racy pool_index accesses
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@google.com: s/pool_index/pool_index_cached/ in stack_depot_fetch()] Link: https://lkml.kernel.org/r/95cf53f0da2c112aa2cc54456cbcd6975c3ff343.1676129911.git.andreyknvl@google.com Link: https://lkml.kernel.org/r/359ac9c13cd0869c56740fb2029f505e41593830.1676063693.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'lib')
-rw-r--r--lib/stackdepot.c17
1 files changed, 13 insertions, 4 deletions
diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index 8c6e4e9cb535..b625090890e1 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -278,8 +278,12 @@ depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc)
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_stack_handle_t handle,
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_stack_handle_t handle,
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];