[PATCH v3] target/s390x/arch_dump: Fix warning for the name field in the PT_NOTE section

[PATCH v3] target/s390x/arch_dump: Fix warning for the name field in the PT_NOTE section

[Thomas Huth]

There is a compiler warning with GCC 9.3 when compiling with
the -fsanitize=thread compiler flag:

 In function 'strncpy',
    inlined from 's390x_write_elf64_notes' at ../target/s390x/arch_dump.c:219:9:
 /usr/include/x86_64-linux-gnu/bits/string_fortified.h:106:10: error:
  '__builtin_strncpy' specified bound 8 equals destination size
  [-Werror=stringop-truncation]

Since the name should always be NUL-terminated, let's use g_strlcpy() to
silence this warning. And while we're at it, also add an assert() to make
sure that the provided names always fit the size field (which is fine for
the current callers, the function is called once with "CORE" and once with
"LINUX" as a name).

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 v3: Do not touch the namesz field

 target/s390x/arch_dump.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/target/s390x/arch_dump.c b/target/s390x/arch_dump.c
index 50fa0ae4b6..cc1330876b 100644
--- a/target/s390x/arch_dump.c
+++ b/target/s390x/arch_dump.c
@@ -212,11 +212,13 @@ static int s390x_write_elf64_notes(const char *note_name,
     int note_size;
     int ret = -1;
 
+    assert(strlen(note_name) < sizeof(note.name));
+
     for (nf = funcs; nf->note_contents_func; nf++) {
         memset(&note, 0, sizeof(note));
         note.hdr.n_namesz = cpu_to_be32(strlen(note_name) + 1);
         note.hdr.n_descsz = cpu_to_be32(nf->contents_size);
-        strncpy(note.name, note_name, sizeof(note.name));
+        g_strlcpy(note.name, note_name, sizeof(note.name));
         (*nf->note_contents_func)(&note, cpu, id);
 
         note_size = sizeof(note) - sizeof(note.contents) + nf->contents_size;
-- 
2.27.0

Re: [PATCH v3] target/s390x/arch_dump: Fix warning for the name field in the PT_NOTE section

[Christian Borntraeger]

On 05.02.21 10:39, Thomas Huth wrote:
> There is a compiler warning with GCC 9.3 when compiling with
> the -fsanitize=thread compiler flag:
> 
>  In function 'strncpy',
>     inlined from 's390x_write_elf64_notes' at ../target/s390x/arch_dump.c:219:9:
>  /usr/include/x86_64-linux-gnu/bits/string_fortified.h:106:10: error:
>   '__builtin_strncpy' specified bound 8 equals destination size
>   [-Werror=stringop-truncation]
> 
> Since the name should always be NUL-terminated, let's use g_strlcpy() to
> silence this warning. And while we're at it, also add an assert() to make
> sure that the provided names always fit the size field (which is fine for
> the current callers, the function is called once with "CORE" and once with
> "LINUX" as a name).
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>

Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>

> ---
>  v3: Do not touch the namesz field
> 
>  target/s390x/arch_dump.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/target/s390x/arch_dump.c b/target/s390x/arch_dump.c
> index 50fa0ae4b6..cc1330876b 100644
> --- a/target/s390x/arch_dump.c
> +++ b/target/s390x/arch_dump.c
> @@ -212,11 +212,13 @@ static int s390x_write_elf64_notes(const char *note_name,
>      int note_size;
>      int ret = -1;
>  
> +    assert(strlen(note_name) < sizeof(note.name));
> +
>      for (nf = funcs; nf->note_contents_func; nf++) {
>          memset(&note, 0, sizeof(note));
>          note.hdr.n_namesz = cpu_to_be32(strlen(note_name) + 1);
>          note.hdr.n_descsz = cpu_to_be32(nf->contents_size);
> -        strncpy(note.name, note_name, sizeof(note.name));
> +        g_strlcpy(note.name, note_name, sizeof(note.name));
>          (*nf->note_contents_func)(&note, cpu, id);
>  
>          note_size = sizeof(note) - sizeof(note.contents) + nf->contents_size;
> 

Re: [PATCH v3] target/s390x/arch_dump: Fix warning for the name field in the PT_NOTE section

[Cornelia Huck]

On Fri,  5 Feb 2021 10:39:21 +0100
Thomas Huth <thuth@redhat.com> wrote:

> There is a compiler warning with GCC 9.3 when compiling with
> the -fsanitize=thread compiler flag:
> 
>  In function 'strncpy',
>     inlined from 's390x_write_elf64_notes' at ../target/s390x/arch_dump.c:219:9:
>  /usr/include/x86_64-linux-gnu/bits/string_fortified.h:106:10: error:
>   '__builtin_strncpy' specified bound 8 equals destination size
>   [-Werror=stringop-truncation]
> 
> Since the name should always be NUL-terminated, let's use g_strlcpy() to
> silence this warning. And while we're at it, also add an assert() to make
> sure that the provided names always fit the size field (which is fine for
> the current callers, the function is called once with "CORE" and once with
> "LINUX" as a name).
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>  v3: Do not touch the namesz field
> 
>  target/s390x/arch_dump.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)

Thanks, applied.