Re: [PATCH kmod 01/13] libkmod: use a dup()'d fd for zlib

[Lucas De Marchi]

On Mon, Feb 12, 2024 at 05:23:02PM GMT, Emil Velikov via B4 Relay wrote:

From: Emil Velikov <emil.l.veli...@gmail.com>

The gzdopen() API used, takes ownership of the fd. To make that more
explicit we clear it (-1) as applicable.

Yet again, kmod has explicit API to return the fd to the user - which
currently is used solely when uncompressed, so we're safe.

Regardless - simply duplicate the fd locally and use that with zlib.

Signed-off-by: Emil Velikov <emil.l.veli...@gmail.com>

Reviewed-by: Lucas De Marchi <lucas.demar...@intel.com>


Lucas De Marchi

---
libkmod/libkmod-file.c | 19 ++++++++++++-------
1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/libkmod/libkmod-file.c b/libkmod/libkmod-file.c
index b138e7e..b97062b 100644
--- a/libkmod/libkmod-file.c
+++ b/libkmod/libkmod-file.c
@@ -317,12 +317,18 @@ static int load_zlib(struct kmod_file *file)
        int err = 0;
        off_t did = 0, total = 0;
        _cleanup_free_ unsigned char *p = NULL;
+       int gzfd;

        errno = 0;
-       file->gzf = gzdopen(file->fd, "rb");
-       if (file->gzf == NULL)
+       gzfd = fcntl(file->fd, F_DUPFD_CLOEXEC, 3);
+       if (gzfd < 0)
+               return -errno;
+
+       file->gzf = gzdopen(gzfd, "rb"); /* takes ownership of the fd */
+       if (file->gzf == NULL) {
+               close(gzfd);
                return -errno;
-       file->fd = -1; /* now owned by gzf due gzdopen() */
+       }

        for (;;) {
                int r;
@@ -359,7 +365,7 @@ static int load_zlib(struct kmod_file *file)
        return 0;

error:
-       gzclose(file->gzf);
+       gzclose(file->gzf); /* closes the gzfd */
        return err;
}

@@ -368,7 +374,7 @@ static void unload_zlib(struct kmod_file *file)
        if (file->gzf == NULL)
                return;
        free(file->memory);
-       gzclose(file->gzf); /* closes file->fd */
+       gzclose(file->gzf);
}

static const char magic_zlib[] = {0x1f, 0x8b};
@@ -535,7 +541,6 @@ void kmod_file_unref(struct kmod_file *file)
        if (file->memory)
                file->ops->unload(file);

-       if (file->fd >= 0)
-               close(file->fd);
+       close(file->fd);
        free(file);
}

--
2.43.0