diff options
| author | Andrey Konovalov <andreyknvl@google.com> | 2023-02-10 22:16:04 +0100 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2023-02-16 20:43:51 -0800 |
| commit | beb3c23c69a91a10f247e93ffef1fcd0209d93e4 (patch) | |
| tree | b5c3d6e4e1d38541fc1e8f298f66e6f741012134 /lib/stackdepot.c | |
| parent | 36aa1e6779c3c6f8e0d4552544214f5cffe3c287 (diff) | |
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/stackdepot.c')
| -rw-r--r-- | lib/stackdepot.c | 17 |
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]; |