perf record: Prevent reading invalid data in record__mmap_read
When record__mmap_read() requires data more than the size of ring buffer, drop those data to avoid accessing invalid memory. This can happen when reading from overwritable ring buffer, which should be avoided. However, check this for robustness. Signed-off-by: Wang Nan <wangnan0@huawei.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Zefan Li <lizefan@huawei.com> Cc: pi3orama@163.com Link: http://lkml.kernel.org/r/1463987628-163563-3-git-send-email-wangnan0@huawei.com Signed-off-by: He Kuang <hekuang@huawei.com> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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@ -40,6 +40,7 @@
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#include <unistd.h>
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#include <sched.h>
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#include <sys/mman.h>
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#include <asm/bug.h>
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struct record {
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@ -98,6 +99,13 @@ static int record__mmap_read(struct record *rec, int idx)
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rec->samples++;
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size = head - old;
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if (size > (unsigned long)(md->mask) + 1) {
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WARN_ONCE(1, "failed to keep up with mmap data. (warn only once)\n");
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md->prev = head;
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perf_evlist__mmap_consume(rec->evlist, idx);
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return 0;
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}
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if ((old & md->mask) + size != (head & md->mask)) {
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buf = &data[old & md->mask];
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