Hi Aaron,
On Thu, Jan 30, 2025 at 09:35:51PM -0500, Aaron Merey wrote:
> process_archive may be called with an fd argument of -1, which
> libelf interprets as "no file opened". However when closing
> the fd process_archive does not check whether the fd is valid
> and may attempt to close an fd of -1.
Nice find. Less syscalls (that do nothing/just error) is always
better. I was puzzled for a moment how this could happen. But there is
a comment in offline.c already that explains:
/* It is ok to pass fd == -1 here, because libelf uses it as a value for
"no file opened" and supports working with files without fd, thanks to
the existence of the elf_memory function. */
Could you apply this patch before enabling valgrind --track-fds-yes?
Thanks,
Mark
> Signed-off-by: Aaron Merey <[email protected]>
> ---
> libdwfl/offline.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/libdwfl/offline.c b/libdwfl/offline.c
> index 24e9e180..dc099d2b 100644
> --- a/libdwfl/offline.c
> +++ b/libdwfl/offline.c
> @@ -271,7 +271,8 @@ process_archive (Dwfl *dwfl, const char *name, const char
> *file_name, int fd,
> zero, that module will close FD. If no modules survived the predicate,
> we are all done with the file right here. */
> if (mod != NULL /* If no modules, caller will clean up. */
> - && elf_end (archive) == 0)
> + && elf_end (archive) == 0
> + && fd >= 0)
> close (fd);
>
> return mod;
> --
> 2.48.1
>
