On 05/13/2013 10:05 AM, Jan Safranek wrote:
> On 05/12/2013 02:08 PM, Ivana Varekova wrote:
>> Seems ok for me, Jan could you look at it pleas?
>> Ivana
>>
>> ----- Original Message -----
>>> From: "Peter Schiffer" <pschi...@redhat.com>
>>> To: libcg-devel@lists.sourceforge.net
>>> Sent: Monday, February 11, 2013 6:09:02 PM
>>> Subject: [Libcg-devel] [PATCH] Make cg_mkdir_p() function compatible with
>>> read-only fs
>>>
>>> mkdir(2) function returns EROFS error even when the path already exists on
>>> the
>>> read only file system, so it is impossible to determine whether the path
>>> already
>>> exists on this kind of fs only be return code from the mkdir(2). To make
>>> cg_mkdir_p() compatible with the ro fs, the function checks whether the path
>>> exists with stat(2) before trying to create it.
>>>
>>> Signed-off-by: Peter Schiffer <pschi...@redhat.com>
>>> ---
>>> 0 files changed
>>>
>>> diff --git a/src/api.c b/src/api.c
>>> index 11cd1b4..4acdc30 100644
>>> --- a/src/api.c
>>> +++ b/src/api.c
>>> @@ -1271,6 +1271,7 @@ int cg_mkdir_p(const char *path)
>>> int i = 0;
>>> char pos;
>>> int ret = 0;
>>> + struct stat st;
>>>
>>> real_path = strdup(path);
>>> if (!real_path) {
>>> @@ -1287,6 +1288,10 @@ int cg_mkdir_p(const char *path)
>>> i++;
>>> pos = real_path[i];
>>> real_path[i] = '\0'; /* Temporarily overwrite "/" */
>>> + if (stat(real_path, &st) == 0) { /* Continue if
>>> dir exists */
>>> + real_path[i] = pos;
>>> + continue;
>>> + }
>
> I think this code is racy. There can be a change between stat() and
> mkdir(). Shouldn't mkdir() return EEXIST is the directory already
> exists? Please check/test it. If it still returns EROFS in this case,
> then I ack this patch, there is no other way how to do it.
>
>>> ret = mkdir(real_path, S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);
>>> real_path[i] = pos;
>>> if (ret) {
>
There is updated version of this patch, which shouldn't be racy, see
below. I can confirm that mkdir() returns EROFS on read-only fs even
when the directory exists.
peter
diff --git a/src/api.c b/src/api.c
index 11cd1b4..b5bbb74 100644
--- a/src/api.c
+++ b/src/api.c
@@ -1270,7 +1270,8 @@ int cg_mkdir_p(const char *path)
char *real_path = NULL;
int i = 0;
char pos;
- int ret = 0;
+ int ret = 0, stat_ret;
+ struct stat st;
real_path = strdup(path);
if (!real_path) {
@@ -1298,6 +1299,14 @@ int cg_mkdir_p(const char *path)
ret = ECGROUPNOTOWNER;
goto done;
default:
+ /* Check if path exists */
+ real_path[i] = '\0';
+ stat_ret = stat(real_path, &st);
+ real_path[i] = pos;
+ if (stat_ret == 0) {
+ ret = 0; /* Path exists */
+ break;
+ }
ret = ECGROUPNOTALLOWED;
goto done;
}
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