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    Subject[PATCH 5.1 062/371] perf jvmti: Address gcc string overflow warning for strncpy()
    Date
    [ Upstream commit 279ab04dbea1370d2eac0f854270369ccaef8a44 ]

    We are getting false positive gcc warning when we compile with gcc9 (9.1.1):

    CC jvmti/libjvmti.o
    In file included from /usr/include/string.h:494,
    from jvmti/libjvmti.c:5:
    In function ‘strncpy’,
    inlined from ‘copy_class_filename.constprop’ at jvmti/libjvmti.c:166:3:
    /usr/include/bits/string_fortified.h:106:10: error: ‘__builtin_strncpy’ specified bound depends on the length of the source argument [-Werror=stringop-overflow=]
    106 | return __builtin___strncpy_chk (__dest, __src, __len, __bos (__dest));
    | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    jvmti/libjvmti.c: In function ‘copy_class_filename.constprop’:
    jvmti/libjvmti.c:165:26: note: length computed here
    165 | size_t file_name_len = strlen(file_name);
    | ^~~~~~~~~~~~~~~~~
    cc1: all warnings being treated as errors

    As per Arnaldo's suggestion use strlcpy(), which does the same thing and keeps
    gcc silent.

    Suggested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
    Signed-off-by: Jiri Olsa <jolsa@kernel.org>
    Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
    Cc: Ben Gainey <ben.gainey@arm.com>
    Cc: Namhyung Kim <namhyung@kernel.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Stephane Eranian <eranian@google.com>
    Link: http://lkml.kernel.org/r/20190531131321.GB1281@krava
    Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    tools/perf/jvmti/libjvmti.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    diff --git a/tools/perf/jvmti/libjvmti.c b/tools/perf/jvmti/libjvmti.c
    index aea7b1fe85aa..c441a34cb1c0 100644
    --- a/tools/perf/jvmti/libjvmti.c
    +++ b/tools/perf/jvmti/libjvmti.c
    @@ -1,5 +1,6 @@
    // SPDX-License-Identifier: GPL-2.0
    #include <linux/compiler.h>
    +#include <linux/string.h>
    #include <sys/types.h>
    #include <stdio.h>
    #include <string.h>
    @@ -162,8 +163,7 @@ copy_class_filename(const char * class_sign, const char * file_name, char * resu
    result[i] = '\0';
    } else {
    /* fallback case */
    - size_t file_name_len = strlen(file_name);
    - strncpy(result, file_name, file_name_len < max_length ? file_name_len : max_length);
    + strlcpy(result, file_name, max_length);
    }
    }

    --
    2.20.1


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