Check the buffer size more precisely to allow buffers for exactly one element provided the base address is already properly aligned. Add a debug store selftest. Reported-by: Stephane Eranian Signed-off-by: Markus Metzger --- arch/x86/kernel/ds.c | 9 7 + 2 - 0 ! arch/x86/kernel/ds_selftest.c | 6 3 + 3 - 0 ! 2 files changed, 10 insertions(+), 5 deletions(-) Index: b/arch/x86/kernel/ds.c =================================================================== --- a/arch/x86/kernel/ds.c +++ b/arch/x86/kernel/ds.c @@ -656,6 +656,7 @@ static int ds_request(struct ds_tracer * { struct ds_context *context; int error; + size_t req_size; error = -EOPNOTSUPP; if (!ds_cfg.sizeof_rec[qual]) @@ -665,9 +666,13 @@ static int ds_request(struct ds_tracer * if (!base) goto out; - /* We need space for alignment adjustments in ds_init_ds_trace(). */ + req_size = ds_cfg.sizeof_rec[qual]; + /* We might need space for alignment adjustments. */ + if (!IS_ALIGNED((unsigned long)base, DS_ALIGNMENT)) + req_size += DS_ALIGNMENT; + error = -EINVAL; - if (size < (DS_ALIGNMENT + ds_cfg.sizeof_rec[qual])) + if (size < req_size) goto out; if (th != (size_t)-1) { Index: b/arch/x86/kernel/ds_selftest.c =================================================================== --- a/arch/x86/kernel/ds_selftest.c +++ b/arch/x86/kernel/ds_selftest.c @@ -16,8 +16,8 @@ #include -#define BUFFER_SIZE 521 /* Intentionally chose an odd size. */ - +#define BUFFER_SIZE 521 /* Intentionally chose an odd size. */ +#define SMALL_BUFFER_SIZE 24 /* A single bts entry. */ struct ds_selftest_bts_conf { struct bts_tracer *tracer; @@ -381,7 +381,7 @@ int ds_selftest_bts(void) conf.suspend = ds_suspend_bts_noirq; conf.resume = ds_resume_bts_noirq; conf.tracer = - ds_request_bts_task(current, buffer, BUFFER_SIZE, + ds_request_bts_task(current, buffer, SMALL_BUFFER_SIZE, NULL, (size_t)-1, BTS_KERNEL); local_irq_save(irq); ds_selftest_bts_cpu(&conf); --