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proc read mm's {arg,env}_{start,end} with mmap semaphore taken. 

Only functions doing more than one read are modified.  Consumeres
happened to deal with possibly changing data, but it does not seem like
a good thing to rely on.

Signed-off-by: Mateusz Guzik <mguzik@redhat.com>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Jarod Wilson <jarod@redhat.com>
Cc: Jan Stancek <jstancek@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Anshuman Khandual <anshuman.linux@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Mateusz Guzik 2016-01-20 15:01:05 -08:00 committed by Linus Torvalds
parent ddf1d398e5
commit a3b609ef9f
2 changed files with 22 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
fs/proc/base.c
View File

@ -953,6 +953,7 @@ static ssize_t environ_read(struct file *file, char __user *buf,
unsigned long src = *ppos;
int ret = 0;
struct mm_struct *mm = file->private_data;
unsigned long env_start, env_end;
if (!mm)
return 0;
@ -964,19 +965,25 @@ static ssize_t environ_read(struct file *file, char __user *buf,
ret = 0;
if (!atomic_inc_not_zero(&mm->mm_users))
goto free;
down_read(&mm->mmap_sem);
env_start = mm->env_start;
env_end = mm->env_end;
up_read(&mm->mmap_sem);
while (count > 0) {
size_t this_len, max_len;
int retval;
if (src >= (mm->env_end - mm->env_start))
if (src >= (env_end - env_start))
break;
this_len = mm->env_end - (mm->env_start + src);
this_len = env_end - (env_start + src);
max_len = min_t(size_t, PAGE_SIZE, count);
this_len = min(max_len, this_len);
retval = access_remote_vm(mm, (mm->env_start + src),
retval = access_remote_vm(mm, (env_start + src),
page, this_len, 0);
if (retval <= 0) {

16
mm/util.c
View File

@ -476,17 +476,25 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen)
int res = 0;
unsigned int len;
struct mm_struct *mm = get_task_mm(task);
unsigned long arg_start, arg_end, env_start, env_end;
if (!mm)
goto out;
if (!mm->arg_end)
goto out_mm; /* Shh! No looking before we're done */
len = mm->arg_end - mm->arg_start;
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);
len = arg_end - arg_start;
if (len > buflen)
len = buflen;
res = access_process_vm(task, mm->arg_start, buffer, len, 0);
res = access_process_vm(task, arg_start, buffer, len, 0);
/*
* If the nul at the end of args has been overwritten, then
@ -497,10 +505,10 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen)
if (len < res) {
res = len;
} else {
len = mm->env_end - mm->env_start;
len = env_end - env_start;
if (len > buflen - res)
len = buflen - res;
res += access_process_vm(task, mm->env_start,
res += access_process_vm(task, env_start,
buffer+res, len, 0);
res = strnlen(buffer, res);
}