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SubjectRe: [PATCH] um: remove uses of variable length arrays
śr., 13 mar 2019 o 10:45 Anton Ivanov
<anton.ivanov@cambridgegreys.com> napisał(a):
>
> On 12/03/2019 13:30, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> >
> > While the affected code is run in user-mode, the build still warns
> > about it. Convert all uses of VLA to dynamic allocations.
> >
> > Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> > ---
> > arch/um/os-Linux/umid.c | 36 +++++++++++++++++++++++++++---------
> > 1 file changed, 27 insertions(+), 9 deletions(-)
> >
> > diff --git a/arch/um/os-Linux/umid.c b/arch/um/os-Linux/umid.c
> > index 998fbb445458..e261656fe9d7 100644
> > --- a/arch/um/os-Linux/umid.c
> > +++ b/arch/um/os-Linux/umid.c
> > @@ -135,12 +135,18 @@ static int remove_files_and_dir(char *dir)
> > */
> > static inline int is_umdir_used(char *dir)
> > {
> > - char file[strlen(uml_dir) + UMID_LEN + sizeof("/pid\0")];
> > - char pid[sizeof("nnnnn\0")], *end;
> > + char pid[sizeof("nnnnn\0")], *end, *file;
> > int dead, fd, p, n, err;
> > + size_t filelen;
> >
> > - n = snprintf(file, sizeof(file), "%s/pid", dir);
> > - if (n >= sizeof(file)) {
> > + err = asprintf(&file, "%s/pid", dir);
> > + if (err < 0)
> > + return 0;
> > +
> > + filelen = strlen(file);
> > +
> > + n = snprintf(file, filelen, "%s/pid", dir);
> > + if (n >= filelen) {
> > printk(UM_KERN_ERR "is_umdir_used - pid filename too long\n");
> > err = -E2BIG;
> > goto out;
> > @@ -185,6 +191,7 @@ static inline int is_umdir_used(char *dir)
> > out_close:
> > close(fd);
> > out:
> > + free(file);
> > return 0;
> > }
> >
> > @@ -210,18 +217,21 @@ static int umdir_take_if_dead(char *dir)
> >
> > static void __init create_pid_file(void)
> > {
> > - char file[strlen(uml_dir) + UMID_LEN + sizeof("/pid\0")];
> > - char pid[sizeof("nnnnn\0")];
> > + char pid[sizeof("nnnnn\0")], *file;
> > int fd, n;
> >
> > - if (umid_file_name("pid", file, sizeof(file)))
> > + file = malloc(strlen(uml_dir) + UMID_LEN + sizeof("/pid\0"));
> > + if (!file)
> > return;
> >
> > + if (umid_file_name("pid", file, sizeof(file)))
> > + goto out;
> > +
> > fd = open(file, O_RDWR | O_CREAT | O_EXCL, 0644);
> > if (fd < 0) {
> > printk(UM_KERN_ERR "Open of machine pid file \"%s\" failed: "
> > "%s\n", file, strerror(errno));
> > - return;
> > + goto out;
> > }
> >
> > snprintf(pid, sizeof(pid), "%d\n", getpid());
> > @@ -231,6 +241,8 @@ static void __init create_pid_file(void)
> > errno);
> >
> > close(fd);
> > +out:
> > + free(file);
> > }
> >
> > int __init set_umid(char *name)
> > @@ -385,13 +397,19 @@ __uml_setup("uml_dir=", set_uml_dir,
> >
> > static void remove_umid_dir(void)
> > {
> > - char dir[strlen(uml_dir) + UMID_LEN + 1], err;
> > + char *dir, err;
> > +
> > + dir = malloc(strlen(uml_dir) + UMID_LEN + 1);
> > + if (!dir)
> > + return;
> >
> > sprintf(dir, "%s%s", uml_dir, umid);
> > err = remove_files_and_dir(dir);
> > if (err)
> > os_warn("%s - remove_files_and_dir failed with err = %d\n",
> > __func__, err);
> > +
> > + free(dir);
> > }
> >
> > __uml_exitcall(remove_umid_dir);
> >
>
> Thanks for bringing it up. It helped me notice that this is actually broken.
>
> PID can be more than 5 digits nowdays.
>
> --

Do you want to take this patch anyway and then apply the fix for the
array on top of that or do you prefer it be fixed before that?

Bart

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