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rlimits: make sure ->rlim_max never grows in sys_setrlimit

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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>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
This commit is contained in:
Oleg Nesterov 2009-09-03 19:21:45 +02:00 committed by Jiri Slaby
parent 5ab46b345e
commit 2fb9d2689a
1 changed files with 8 additions and 7 deletions
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15
kernel/sys.c
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@ -1283,10 +1283,6 @@ SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim)
return -EFAULT; return -EFAULT;
if (new_rlim.rlim_cur > new_rlim.rlim_max) if (new_rlim.rlim_cur > new_rlim.rlim_max)
return -EINVAL; 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) if (resource == RLIMIT_NOFILE && new_rlim.rlim_max > sysctl_nr_open)
return -EPERM; return -EPERM;
@ -1304,11 +1300,16 @@ SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim)
new_rlim.rlim_cur = 1; new_rlim.rlim_cur = 1;
} }
old_rlim = current->signal->rlim + resource;
task_lock(current->group_leader); task_lock(current->group_leader);
*old_rlim = new_rlim; if (new_rlim.rlim_max > old_rlim->rlim_max &&
!capable(CAP_SYS_RESOURCE))
retval = -EPERM;
else
*old_rlim = new_rlim;
task_unlock(current->group_leader); task_unlock(current->group_leader);
if (resource != RLIMIT_CPU) if (retval || resource != RLIMIT_CPU)
goto out; goto out;
/* /*
@ -1322,7 +1323,7 @@ SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim)
update_rlimit_cpu(current, new_rlim.rlim_cur); update_rlimit_cpu(current, new_rlim.rlim_cur);
out: out:
return 0; return retval;
} }
/* /*