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Message-Id: <200901262004.16364.arnd@arndb.de>
Date: Mon, 26 Jan 2009 20:04:15 +0100
From: Arnd Bergmann <arnd@...db.de>
To: narendramind@...kesource.com
Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
torvalds@...l.org, linux-abi@...r.kernel.org,
linux-arch@...r.kernel.org
Subject: Re: [PATCH 1/1] x86: syscalls: sys_setrlimit64/sys_getrlimit64 calls to provide FSIZE limits > 2^32-1
On Friday 23 January 2009, narendramind@...kesource.com wrote:
>
> The solution to this problem would require new setrlimit64() and
> getrlimit64() system calls on x86, and the existing 32-bit system calls
> would need to be retained so that existing binaries would still run.
When adding new syscalls, please Cc: linux-abi@...r.kernel.org and
linux-arch@...r.kernel.org to get attention from all parties that are
involved.
> diff -uNrp -X linux-2.6.29-rc2/Documentation/dontdiff linux-2.6.29-rc2/arch/x86/kernel/syscall_table_32.S linux-2.6.29-rc2-rlim64/arch/x86/kernel/syscall_table_32.S
> --- linux-2.6.29-rc2/arch/x86/kernel/syscall_table_32.S 2009-01-17 09:54:06.000000000 +0530
> +++ linux-2.6.29-rc2-rlim64/arch/x86/kernel/syscall_table_32.S 2009-01-17 19:15:52.000000000 +0530
> @@ -332,3 +332,5 @@ ENTRY(sys_call_table)
> .long sys_dup3 /* 330 */
> .long sys_pipe2
> .long sys_inotify_init1
> + .long sys_setrlimit64
> + .long sys_getrlimit64
This only adds the calls to the native 32 bit build, but not to
the 32-on-64 compat code in arch/x86/ia32/ia32entry.S (or any of the
other architectures.
> --- linux-2.6.29-rc2/kernel/ChangeLog 1970-01-01 05:30:00.000000000 +0530
> +++ linux-2.6.29-rc2-rlim64/kernel/ChangeLog 2009-01-17 19:15:50.000000000 +0530
> @@ -0,0 +1,10 @@
> +2008-01-17 Narendra Prasad <narendramind@...il.com>
> + Problem Description:
> + The following issue affects the setrlimit() and getrlimit() system calls on Linux 2.6.13 (and earlier) on x86.
> + The Problem is filed at kernel.org bug 5042 (http://bugzilla.kernel.org/show_bug.cgi?id=5042)
> + Design Approach:
> + Add two system calls sys_setrlimit64()/sys_getrlimit64().
> + And a type 'struct rlimit64' to accomodate more no. of limits <= 2^64-1
> + Implementation Details:
> + Inclusions: struct rlimit64, struct rlimit64
> + rlim64[RLIM64_NRLIMITS] to task_struct
The changelog is the git history, please don't add other files for this.
> +SYSCALL_DEFINE2(setrlimit64, unsigned int, resource,
> + struct rlimit64 __user *, rlim)
> +{
> + struct rlimit64 new_rlim;
> + struct rlimit *old_rlim, new_value;
> + unsigned long it_prof_secs;
> + int retval;
> +
> + if (resource >= RLIM_NLIMITS)
> + return -EINVAL;
> + if (copy_from_user(&new_rlim, rlim, sizeof(*rlim)))
> + return -EFAULT;
> +
> + if (resource == RLIMIT_FSIZE) {
> + struct rlimit64 *old_rlim;
> + struct rlimit *old_value;
> +
> + old_rlim = current->signal->rlim64 + resource;
> + if (((new_rlim.rlim64_cur > old_rlim->rlim64_max) ||
> + (new_rlim.rlim64_max > old_rlim->rlim64_max)) &&
> + !capable(CAP_SYS_RESOURCE))
> + return -EPERM;
> + *old_rlim = new_rlim;
> + if (new_rlim.rlim64_cur > RLIM_INFINITY)
> + new_rlim.rlim64_cur = RLIM_INFINITY;
> + if (new_rlim.rlim64_max > RLIM_INFINITY)
> + new_rlim.rlim64_max = RLIM_INFINITY;
> +
> + task_lock(current->group_leader);
> + old_value = (current->signal->rlim + resource);
> + old_value->rlim_max = new_rlim.rlim64_max;
> + old_value->rlim_cur = new_rlim.rlim64_cur;
> + task_unlock(current->group_leader);
> +
> + return 0;
> + }
> +
> + old_rlim = current->signal->rlim + resource;
> + if (new_rlim.rlim64_cur > RLIM_INFINITY)
> + new_rlim.rlim64_cur = RLIM_INFINITY;
> + if (new_rlim.rlim64_max > RLIM_INFINITY)
> + new_rlim.rlim64_max = RLIM_INFINITY;
> + if (((new_rlim.rlim64_cur > old_rlim->rlim_max) ||
> + (new_rlim.rlim64_max > old_rlim->rlim_max)) &&
> + !capable(CAP_SYS_RESOURCE))
> + return -EPERM;
> + if (resource == RLIMIT_NOFILE) {
> + if (new_rlim.rlim64_cur > INR_OPEN ||
> + new_rlim.rlim64_max > INR_OPEN)
> + return -EPERM;
> + }
> + new_value.rlim_max = new_rlim.rlim64_max;
> + new_value.rlim_cur = new_rlim.rlim64_cur;
> + retval = security_task_setrlimit(resource, &new_value);
> + if (retval)
> + return retval;
> +
> + if (resource == RLIMIT_CPU && new_value.rlim_cur == 0) {
> + /*
> + * The caller is asking for an immediate RLIMIT_CPU
> + * expiry. But we use the zero value to mean "it was
> + * never set". So let's cheat and make it one second
> + * instead
> + */
> + new_value.rlim_cur = 1;
> + }
> +
> + task_lock(current->group_leader);
> + *old_rlim = new_value;
> + task_unlock(current->group_leader);
> +
> + if (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
> + * very long-standing error, and fixing it now risks breakage of
> + * applications, so we live with it
> + */
> + if (new_value.rlim_cur == RLIM_INFINITY)
> + goto out;
> +
> + it_prof_secs = cputime_to_secs(current->signal->it_prof_expires);
> + if (it_prof_secs == 0 || new_value.rlim_cur <= it_prof_secs) {
> + unsigned long rlim_cur = new_value.rlim_cur;
> + cputime_t cputime;
> +
> + cputime = secs_to_cputime(rlim_cur);
> + read_lock(&tasklist_lock);
> + spin_lock_irq(¤t->sighand->siglock);
> + set_process_cpu_timer(current, CPUCLOCK_PROF, &cputime, NULL);
> + spin_unlock_irq(¤t->sighand->siglock);
> + read_unlock(&tasklist_lock);
> + }
> +out:
> + return 0;
> +}
This function is rather long, and duplicates most of the existing
set_rlimit syscall. You should consolidate the two so you get no
duplication. You can probably add a
static do_setrlimit(unsigned int resource, struct rlimit64 *rlim);
helper function that gets called by both setrlimit and setrlimit64
(also compat_sys_setrlimit) after the copy_from_user().
Arnd <><
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