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    SubjectRe: [PATCH v1 1/4] perf tools: Prevent out-of-bounds access to registers
    On Wed, Dec 01, 2021 at 12:33:29PM +0000, German Gomez wrote:
    > The size of the cache of register values is arch-dependant
    > (PERF_REGS_MAX). This has the potential of causing an out-of-bounds
    > access in the function "perf_reg_value" if the local architecture
    > contains less registers than the one the perf.data file was recorded on.
    >
    > Since the maximum number of registers is bound by the bitmask "u64
    > cache_mask", and the size of the cache when running under x86 systems is
    > 64 already, fix the size to 64 and add a range-check to the function
    > "perf_reg_value" to prevent out-of-bounds access.
    >
    > Signed-off-by: German Gomez <german.gomez@arm.com>

    Acked-by: Jiri Olsa <jolsa@redhat.com>

    thanks,
    jirka

    > ---
    > tools/perf/util/event.h | 5 ++++-
    > tools/perf/util/perf_regs.c | 3 +++
    > 2 files changed, 7 insertions(+), 1 deletion(-)
    >
    > diff --git a/tools/perf/util/event.h b/tools/perf/util/event.h
    > index 95ffed663..c59331eea 100644
    > --- a/tools/perf/util/event.h
    > +++ b/tools/perf/util/event.h
    > @@ -44,13 +44,16 @@ struct perf_event_attr;
    > /* perf sample has 16 bits size limit */
    > #define PERF_SAMPLE_MAX_SIZE (1 << 16)
    >
    > +/* number of register is bound by the number of bits in regs_dump::mask (64) */
    > +#define PERF_SAMPLE_REGS_CACHE_SIZE (8 * sizeof(u64))
    > +
    > struct regs_dump {
    > u64 abi;
    > u64 mask;
    > u64 *regs;
    >
    > /* Cached values/mask filled by first register access. */
    > - u64 cache_regs[PERF_REGS_MAX];
    > + u64 cache_regs[PERF_SAMPLE_REGS_CACHE_SIZE];
    > u64 cache_mask;
    > };
    >
    > diff --git a/tools/perf/util/perf_regs.c b/tools/perf/util/perf_regs.c
    > index 5ee47ae15..06a7461ba 100644
    > --- a/tools/perf/util/perf_regs.c
    > +++ b/tools/perf/util/perf_regs.c
    > @@ -25,6 +25,9 @@ int perf_reg_value(u64 *valp, struct regs_dump *regs, int id)
    > int i, idx = 0;
    > u64 mask = regs->mask;
    >
    > + if ((u64)id >= PERF_SAMPLE_REGS_CACHE_SIZE)
    > + return -EINVAL;
    > +
    > if (regs->cache_mask & (1ULL << id))
    > goto out;
    >
    > --
    > 2.25.1
    >

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