Commit c2c0bb44 authored by Alexey Dobriyan's avatar Alexey Dobriyan Committed by Linus Torvalds
Browse files

proc: fix PAGE_SIZE limit of /proc/$PID/cmdline

/proc/$PID/cmdline truncates output at PAGE_SIZE. It is easy to see with

	$ cat /proc/self/cmdline $(seq 1037) 2>/dev/null

However, command line size was never limited to PAGE_SIZE but to 128 KB
and relatively recently limitation was removed altogether.

People noticed and ask questions:
http://stackoverflow.com/questions/199130/how-do-i-increase-the-proc-pid-cmdline-4096-byte-limit



seq file interface is not OK, because it kmalloc's for whole output and
open + read(, 1) + sleep will pin arbitrary amounts of kernel memory.  To
not do that, limit must be imposed which is incompatible with arbitrary
sized command lines.

I apologize for hairy code, but this it direct consequence of command line
layout in memory and hacks to support things like "init [3]".

The loops are "unrolled" otherwise it is either macros which hide control
flow or functions with 7-8 arguments with equal line count.

There should be real setproctitle(2) or something.

[akpm@linux-foundation.org: fix a billion min() warnings]
Signed-off-by: default avatarAlexey Dobriyan <adobriyan@gmail.com>
Tested-by: default avatarJarod Wilson <jarod@redhat.com>
Acked-by: default avatarJarod Wilson <jarod@redhat.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Jan Stancek <jstancek@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4a00e9df
......@@ -196,18 +196,205 @@ static int proc_root_link(struct dentry *dentry, struct path *path)
return result;
}
static int proc_pid_cmdline(struct seq_file *m, struct pid_namespace *ns,
struct pid *pid, struct task_struct *task)
static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf,
size_t _count, loff_t *pos)
{
struct task_struct *tsk;
struct mm_struct *mm;
char *page;
unsigned long count = _count;
unsigned long arg_start, arg_end, env_start, env_end;
unsigned long len1, len2, len;
unsigned long p;
char c;
ssize_t rv;
BUG_ON(*pos < 0);
tsk = get_proc_task(file_inode(file));
if (!tsk)
return -ESRCH;
mm = get_task_mm(tsk);
put_task_struct(tsk);
if (!mm)
return 0;
/* Check if process spawned far enough to have cmdline. */
if (!mm->env_end) {
rv = 0;
goto out_mmput;
}
page = (char *)__get_free_page(GFP_TEMPORARY);
if (!page) {
rv = -ENOMEM;
goto out_mmput;
}
down_read(&mm->mmap_sem);
arg_start = mm->arg_start;
arg_end = mm->arg_end;
env_start = mm->env_start;
env_end = mm->env_end;
up_read(&mm->mmap_sem);
BUG_ON(arg_start > arg_end);
BUG_ON(env_start > env_end);
len1 = arg_end - arg_start;
len2 = env_end - env_start;
/*
* Rely on struct seq_operations::show() being called once
* per internal buffer allocation. See single_open(), traverse().
* Inherently racy -- command line shares address space
* with code and data.
*/
BUG_ON(m->size < PAGE_SIZE);
m->count += get_cmdline(task, m->buf, PAGE_SIZE);
return 0;
rv = access_remote_vm(mm, arg_end - 1, &c, 1, 0);
if (rv <= 0)
goto out_free_page;
rv = 0;
if (c == '\0') {
/* Command line (set of strings) occupies whole ARGV. */
if (len1 <= *pos)
goto out_free_page;
p = arg_start + *pos;
len = len1 - *pos;
while (count > 0 && len > 0) {
unsigned int _count;
int nr_read;
_count = min3(count, len, PAGE_SIZE);
nr_read = access_remote_vm(mm, p, page, _count, 0);
if (nr_read < 0)
rv = nr_read;
if (nr_read <= 0)
goto out_free_page;
if (copy_to_user(buf, page, nr_read)) {
rv = -EFAULT;
goto out_free_page;
}
p += nr_read;
len -= nr_read;
buf += nr_read;
count -= nr_read;
rv += nr_read;
}
} else {
/*
* Command line (1 string) occupies ARGV and maybe
* extends into ENVP.
*/
if (len1 + len2 <= *pos)
goto skip_argv_envp;
if (len1 <= *pos)
goto skip_argv;
p = arg_start + *pos;
len = len1 - *pos;
while (count > 0 && len > 0) {
unsigned int _count, l;
int nr_read;
bool final;
_count = min3(count, len, PAGE_SIZE);
nr_read = access_remote_vm(mm, p, page, _count, 0);
if (nr_read < 0)
rv = nr_read;
if (nr_read <= 0)
goto out_free_page;
/*
* Command line can be shorter than whole ARGV
* even if last "marker" byte says it is not.
*/
final = false;
l = strnlen(page, nr_read);
if (l < nr_read) {
nr_read = l;
final = true;
}
if (copy_to_user(buf, page, nr_read)) {
rv = -EFAULT;
goto out_free_page;
}
p += nr_read;
len -= nr_read;
buf += nr_read;
count -= nr_read;
rv += nr_read;
if (final)
goto out_free_page;
}
skip_argv:
/*
* Command line (1 string) occupies ARGV and
* extends into ENVP.
*/
if (len1 <= *pos) {
p = env_start + *pos - len1;
len = len1 + len2 - *pos;
} else {
p = env_start;
len = len2;
}
while (count > 0 && len > 0) {
unsigned int _count, l;
int nr_read;
bool final;
_count = min3(count, len, PAGE_SIZE);
nr_read = access_remote_vm(mm, p, page, _count, 0);
if (nr_read < 0)
rv = nr_read;
if (nr_read <= 0)
goto out_free_page;
/* Find EOS. */
final = false;
l = strnlen(page, nr_read);
if (l < nr_read) {
nr_read = l;
final = true;
}
if (copy_to_user(buf, page, nr_read)) {
rv = -EFAULT;
goto out_free_page;
}
p += nr_read;
len -= nr_read;
buf += nr_read;
count -= nr_read;
rv += nr_read;
if (final)
goto out_free_page;
}
skip_argv_envp:
;
}
out_free_page:
free_page((unsigned long)page);
out_mmput:
mmput(mm);
if (rv > 0)
*pos += rv;
return rv;
}
static const struct file_operations proc_pid_cmdline_ops = {
.read = proc_pid_cmdline_read,
.llseek = generic_file_llseek,
};
static int proc_pid_auxv(struct seq_file *m, struct pid_namespace *ns,
struct pid *pid, struct task_struct *task)
{
......@@ -2572,7 +2759,7 @@ static const struct pid_entry tgid_base_stuff[] = {
#ifdef CONFIG_HAVE_ARCH_TRACEHOOK
ONE("syscall", S_IRUSR, proc_pid_syscall),
#endif
ONE("cmdline", S_IRUGO, proc_pid_cmdline),
REG("cmdline", S_IRUGO, proc_pid_cmdline_ops),
ONE("stat", S_IRUGO, proc_tgid_stat),
ONE("statm", S_IRUGO, proc_pid_statm),
REG("maps", S_IRUGO, proc_pid_maps_operations),
......@@ -2918,7 +3105,7 @@ static const struct pid_entry tid_base_stuff[] = {
#ifdef CONFIG_HAVE_ARCH_TRACEHOOK
ONE("syscall", S_IRUSR, proc_pid_syscall),
#endif
ONE("cmdline", S_IRUGO, proc_pid_cmdline),
REG("cmdline", S_IRUGO, proc_pid_cmdline_ops),
ONE("stat", S_IRUGO, proc_tid_stat),
ONE("statm", S_IRUGO, proc_pid_statm),
REG("maps", S_IRUGO, proc_tid_maps_operations),
......
Supports Markdown
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment