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SubjectRe: [PATCH] um: remove uses of variable length arrays
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On 14/03/2019 13:33, Bartosz Golaszewski wrote:
> 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
>
I am OK to take it as is and have the PID length fixed after that.

--
Anton R. Ivanov
Cambridgegreys Limited. Registered in England. Company Number 10273661
https://www.cambridgegreys.com/

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