Jan Kara <jack@xxxxxxx> writes:
> On Wed 04-08-21 12:06:03, Gabriel Krisman Bertazi wrote:
>> Instead of failing, encode an invalid file handler in fanotify_encode_fh
>> if no inode is provided. This bogus file handler will be reported by
>> FAN_FS_ERROR for non-inode errors.
>>
>> Also adjust the single caller that might rely on failure after passing
>> an empty inode.
>
> It is not 'file handler' but rather 'file handle' - several times in the
> changelog and in subject :).
>
>> Suggested-by: Amir Goldstein <amir73il@xxxxxxxxx>
>> Signed-off-by: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
>> ---
>> fs/notify/fanotify/fanotify.c | 39 ++++++++++++++++++++---------------
>> fs/notify/fanotify/fanotify.h | 6 ++++--
>> 2 files changed, 26 insertions(+), 19 deletions(-)
>>
>> diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
>> index 0d6ba218bc01..456c60107d88 100644
>> --- a/fs/notify/fanotify/fanotify.c
>> +++ b/fs/notify/fanotify/fanotify.c
>> @@ -349,12 +349,6 @@ static int fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode,
>> void *buf = fh->buf;
>> int err;
>>
>> - fh->type = FILEID_ROOT;
>> - fh->len = 0;
>> - fh->flags = 0;
>> - if (!inode)
>> - return 0;
>> -
>
> I'd keep the fh->flags initialization here. Otherwise it will not be
> initialized on some error returns.
>
>> @@ -363,8 +357,9 @@ static int fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode,
>> if (fh_len < 4 || WARN_ON_ONCE(fh_len % 4))
>> goto out_err;
>>
>> - /* No external buffer in a variable size allocated fh */
>> - if (gfp && fh_len > FANOTIFY_INLINE_FH_LEN) {
>> + fh->flags = 0;
>> + /* No external buffer in a variable size allocated fh or null fh */
>> + if (inode && gfp && fh_len > FANOTIFY_INLINE_FH_LEN) {
>> /* Treat failure to allocate fh as failure to encode fh */
>> err = -ENOMEM;
>> ext_buf = kmalloc(fh_len, gfp);
>> @@ -376,14 +371,24 @@ static int fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode,
>> fh->flags |= FANOTIFY_FH_FLAG_EXT_BUF;
>> }
>>
>> - dwords = fh_len >> 2;
>> - type = exportfs_encode_inode_fh(inode, buf, &dwords, NULL);
>> - err = -EINVAL;
>> - if (!type || type == FILEID_INVALID || fh_len != dwords << 2)
>> - goto out_err;
>> -
>> - fh->type = type;
>> - fh->len = fh_len;
>> + if (inode) {
>> + dwords = fh_len >> 2;
>> + type = exportfs_encode_inode_fh(inode, buf, &dwords, NULL);
>> + err = -EINVAL;
>> + if (!type || type == FILEID_INVALID || fh_len != dwords << 2)
>> + goto out_err;
>> + fh->type = type;
>> + fh->len = fh_len;
>> + } else {
>> + /*
>> + * Invalid FHs are used on FAN_FS_ERROR for errors not
>> + * linked to any inode. Caller needs to guarantee the fh
>> + * has at least FANOTIFY_NULL_FH_LEN bytes of space.
>> + */
>> + fh->type = FILEID_INVALID;
>> + fh->len = FANOTIFY_NULL_FH_LEN;
>> + memset(buf, 0, FANOTIFY_NULL_FH_LEN);
>> + }
>
> Maybe it will become clearer later during the series but why do you set
> fh->len to FANOTIFY_NULL_FH_LEN and not 0?
Jan,
That is how we encode a NULL file handle (i.e. superblock error). Amir
suggested it would be an invalid FILEID_INVALID, with a zeroed handle of
size 8. I will improve the comment on the next iteration.
--
Gabriel Krisman Bertazi
