Messages in this thread Patch in this message | | | Date | Thu, 3 Sep 2009 19:21:45 +0200 | From | Oleg Nesterov <> | Subject | [PATCH 1/1] sys_setrlimit: make sure ->rlim_max never grows |
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Mostly preparation for Jiri's changes, but probably makes sense anyway.
sys_setrlimit() checks new_rlim.rlim_max <= old_rlim->rlim_max, but when it takes task_lock() old_rlim->rlim_max can be already lowered. Move this check under task_lock().
Currently this is not important, we can only race with our sub-thread, this means the application is stupid. But when we change the code to allow the update of !current task's limits, it becomes important to make sure ->rlim_max can be lowered "reliably" even if we race with the application doing sys_setrlimit().
Signed-off-by: Oleg Nesterov <oleg@redhat.com> ---
kernel/sys.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-)
--- WAIT/kernel/sys.c~SETRLIMIT 2009-06-17 14:11:26.000000000 +0200 +++ WAIT/kernel/sys.c 2009-09-03 19:01:48.000000000 +0200 @@ -1247,10 +1247,6 @@ SYSCALL_DEFINE2(setrlimit, unsigned int, return -EFAULT; if (new_rlim.rlim_cur > new_rlim.rlim_max) return -EINVAL; - old_rlim = current->signal->rlim + resource; - if ((new_rlim.rlim_max > old_rlim->rlim_max) && - !capable(CAP_SYS_RESOURCE)) - return -EPERM; if (resource == RLIMIT_NOFILE && new_rlim.rlim_max > sysctl_nr_open) return -EPERM; @@ -1268,13 +1264,17 @@ SYSCALL_DEFINE2(setrlimit, unsigned int, new_rlim.rlim_cur = 1; } + old_rlim = current->signal->rlim + resource; task_lock(current->group_leader); - *old_rlim = new_rlim; + if ((new_rlim.rlim_max <= old_rlim->rlim_max) || + capable(CAP_SYS_RESOURCE)) + *old_rlim = new_rlim; + else + retval = -EPERM; task_unlock(current->group_leader); - if (resource != RLIMIT_CPU) + if (retval || resource != RLIMIT_CPU) goto out; - /* * RLIMIT_CPU handling. Note that the kernel fails to return an error * code if it rejected the user's attempt to set RLIMIT_CPU. This is a @@ -1286,7 +1286,7 @@ SYSCALL_DEFINE2(setrlimit, unsigned int, update_rlimit_cpu(new_rlim.rlim_cur); out: - return 0; + return retval; } /*
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