The patch titled
Subject: proc read mm's {arg,env}_{start,end} with mmap semaphore taken.
has been added to the -mm tree. Its filename is
proc-read-mms-argenv_startend-with-mmap-semaphore-taken.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/proc-read-mms-argenv_startend-with-mmap-semaphore-taken.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/proc-read-mms-argenv_startend-with-mmap-semaphore-taken.patch
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------------------------------------------------------
From: Mateusz Guzik <mguzik@xxxxxxxxxx>
Subject: 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@xxxxxxxxxx>
Acked-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: Jarod Wilson <jarod@xxxxxxxxxx>
Cc: Jan Stancek <jstancek@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Anshuman Khandual <anshuman.linux@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/base.c | 13 ++++++++++---
mm/util.c | 16 ++++++++++++----
2 files changed, 22 insertions(+), 7 deletions(-)
diff -puN fs/proc/base.c~proc-read-mms-argenv_startend-with-mmap-semaphore-taken fs/proc/base.c
--- a/fs/proc/base.c~proc-read-mms-argenv_startend-with-mmap-semaphore-taken
+++ a/fs/proc/base.c
@@ -953,6 +953,7 @@ static ssize_t environ_read(struct file
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
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) {
diff -puN mm/util.c~proc-read-mms-argenv_startend-with-mmap-semaphore-taken mm/util.c
--- a/mm/util.c~proc-read-mms-argenv_startend-with-mmap-semaphore-taken
+++ a/mm/util.c
@@ -475,17 +475,25 @@ int get_cmdline(struct task_struct *task
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
@@ -496,10 +504,10 @@ int get_cmdline(struct task_struct *task
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);
}
_
Patches currently in -mm which might be from mguzik@xxxxxxxxxx are
prctl-take-mmap-sem-for-writing-to-protect-against-others.patch
proc-read-mms-argenv_startend-with-mmap-semaphore-taken.patch
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