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

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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
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16
mm/util.c
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@@ -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);
}