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    Subject[PATCH AUTOSEL for 4.9 071/219] perf buildid: Do not assume that readlink() returns a null terminated string
    Date
    From: Tommi Rantala <tommi.t.rantala@nokia.com>

    [ Upstream commit 5a2342111c68e623e27ee7ea3d0492d8dad6bda0 ]

    Valgrind was complaining:

    $ valgrind ./perf list >/dev/null
    ==11643== Memcheck, a memory error detector
    ==11643== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
    ==11643== Using Valgrind-3.12.0 and LibVEX; rerun with -h for copyright info
    ==11643== Command: ./perf list
    ==11643==
    ==11643== Conditional jump or move depends on uninitialised value(s)
    ==11643== at 0x4C30620: rindex (vg_replace_strmem.c:199)
    ==11643== by 0x49DAA9: build_id_cache__origname (build-id.c:198)
    ==11643== by 0x49E1C7: build_id_cache__valid_id (build-id.c:222)
    ==11643== by 0x49E1C7: build_id_cache__list_all (build-id.c:507)
    ==11643== by 0x4B9C8F: print_sdt_events (parse-events.c:2067)
    ==11643== by 0x4BB0B3: print_events (parse-events.c:2313)
    ==11643== by 0x439501: cmd_list (builtin-list.c:53)
    ==11643== by 0x497150: run_builtin (perf.c:359)
    ==11643== by 0x428CE0: handle_internal_command (perf.c:421)
    ==11643== by 0x428CE0: run_argv (perf.c:467)
    ==11643== by 0x428CE0: main (perf.c:614)
    [...]

    Additionally, a zero length result from readlink() is not very interesting.

    Signed-off-by: Tommi Rantala <tommi.t.rantala@nokia.com>
    Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Link: http://lkml.kernel.org/r/20170322130624.21881-3-tommi.t.rantala@nokia.com
    Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    ---
    tools/perf/util/build-id.c | 6 +++++-
    1 file changed, 5 insertions(+), 1 deletion(-)

    diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
    index e528c40739cc..993ef2762508 100644
    --- a/tools/perf/util/build-id.c
    +++ b/tools/perf/util/build-id.c
    @@ -182,13 +182,17 @@ char *build_id_cache__origname(const char *sbuild_id)
    char buf[PATH_MAX];
    char *ret = NULL, *p;
    size_t offs = 5; /* == strlen("../..") */
    + ssize_t len;

    linkname = build_id_cache__linkname(sbuild_id, NULL, 0);
    if (!linkname)
    return NULL;

    - if (readlink(linkname, buf, PATH_MAX) < 0)
    + len = readlink(linkname, buf, sizeof(buf) - 1);
    + if (len <= 0)
    goto out;
    + buf[len] = '\0';
    +
    /* The link should be "../..<origpath>/<sbuild_id>" */
    p = strrchr(buf, '/'); /* Cut off the "/<sbuild_id>" */
    if (p && (p > buf + offs)) {
    --
    2.14.1
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