On 22 October 2014 09:55, Oleg Nesterov <oleg@xxxxxxxxxx> wrote:
> On 10/21, Victor Kamensky wrote:
>>
>> +static int dump_write_last_byte(struct coredump_params *cprm)
>> +{
>> + char lastbyte = 0;
>> + struct file *file = cprm->file;
>> +
>> + if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
>> + if (dump_interrupted() ||
>> + file->f_op->llseek(file, -1, SEEK_CUR) < 0)
>> + return 0;
>> + if (!dump_emit(cprm, &lastbyte, 1))
>> + return 0;
>> + }
>> + return 1;
>> +}
>
> Perhaps do_truncate(cprm.file->f_path.dentry, ->f_pos) makes more sense?
>
> and unless I missed something cprm->last_op_status can be avoided, we can
> simply check f_pos != i_size_read() at the end?
Oleg, nice advise! Thanks.
So the whole fix becomes something like this:
diff --git a/fs/coredump.c b/fs/coredump.c
index a93f7e6..8c17f1d 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -664,6 +664,14 @@ void do_coredump(const siginfo_t *siginfo)
if (!dump_interrupted()) {
file_start_write(cprm.file);
core_dumped = binfmt->core_dump(&cprm);
+ /*
+ * If last operation was dump_skip with llseek, we need to
+ * truncate file up to f_pos to match expected size.
+ */
+ if (!ispipe &&
+ (cprm.file->f_pos > i_size_read(file_inode(cprm.file))))
+ do_truncate(cprm.file->f_path.dentry,
+ cprm.file->f_pos, 0, cprm.file);
file_end_write(cprm.file);
}
if (ispipe && core_pipe_limit)
May I use your name with Suggested-by tag?
Thanks,
Victor
> Oleg.
>
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