Messages in this thread Patch in this message | | | Date | Fri, 20 Nov 2009 03:11:02 +0100 | From | Oleg Nesterov <> | Subject | acct_file_reopen() && do_acct_process() (Was: [PATCH 0/3] extend get/setrlimit to support setting rlimits external to a process (v7)) |
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On 11/19, Jiri Slaby wrote: > > On 11/19/2009 12:15 AM, Oleg Nesterov wrote: > > On 11/18, Jiri Slaby wrote: > >> > >> kernel/acct.c: > >> /* > >> * Accounting records are not subject to resource limits. > >> */ > >> flim = current->signal->rlim[RLIMIT_FSIZE].rlim_cur; > >> current->signal->rlim[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY; > >> file->f_op->write(file, (char *)&ac, > >> sizeof(acct_t), &file->f_pos); > >> current->signal->rlim[RLIMIT_FSIZE].rlim_cur = flim; > >> > >> It means that threads of the process with PACCT caps have unlimited file > >> size for a short while. If there is setrlimit in between, it gets wiped > >> out as well. > > > > This is called when the whole thread-group exits, there are no > > live threads except current. > > Not really, it is called from umount, sys_acct and other paths.
Hmm. you are right. Do you know why acct_file_reopen() does
if (old_acct) do_acct_process();
???
This looks just strange. What is the point ? If the caller doesn't exit, we shouldn't account it?
And this is just wrong, no? Even if we forget about rlim, since do_acct_process() does override_creds() + revert_creds(), any __task_cred() in between is fooled?
Probably I greatly misread something in acct.c, otherwise I can't see why, say, mntput() should ever record the caller in acct file.
IOW: could someone explain why the patch below is wrong?
Oleg.
--- a/kernel/acct.c +++ b/kernel/acct.c @@ -206,7 +206,6 @@ static void acct_file_reopen(struct bsd_ if (old_acct) { mnt_unpin(old_acct->f_path.mnt); spin_unlock(&acct_lock); - do_acct_process(acct, old_ns, old_acct); filp_close(old_acct, NULL); spin_lock(&acct_lock); }
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