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-rw-r--r--fs/proc/base.c8
-rw-r--r--include/linux/mm_types.h2
-rw-r--r--kernel/fork.c1
-rw-r--r--kernel/sys.c10
-rw-r--r--mm/init-mm.c1
5 files changed, 16 insertions, 6 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c
index e16afc80f810..c7402cb76f11 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -233,12 +233,12 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf,
goto out_mmput;
}
- down_read(&mm->mmap_sem);
+ spin_lock(&mm->arg_lock);
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);
+ spin_unlock(&mm->arg_lock);
BUG_ON(arg_start > arg_end);
BUG_ON(env_start > env_end);
@@ -990,10 +990,10 @@ static ssize_t environ_read(struct file *file, char __user *buf,
if (!atomic_inc_not_zero(&mm->mm_users))
goto free;
- down_read(&mm->mmap_sem);
+ spin_lock(&mm->arg_lock);
env_start = mm->env_start;
env_end = mm->env_end;
- up_read(&mm->mmap_sem);
+ spin_unlock(&mm->arg_lock);
while (count > 0) {
size_t this_len, max_len;
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 29c17fae9bbf..1019e8d3c88f 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -442,6 +442,8 @@ struct mm_struct {
unsigned long exec_vm; /* VM_EXEC & ~VM_WRITE */
unsigned long stack_vm; /* VM_GROWSUP/DOWN */
unsigned long def_flags;
+
+ spinlock_t arg_lock; /* protect the below fields */
unsigned long start_code, end_code, start_data, end_data;
unsigned long start_brk, brk, start_stack;
unsigned long arg_start, arg_end, env_start, env_end;
diff --git a/kernel/fork.c b/kernel/fork.c
index a21adc0155b9..c25ebf6dd7f9 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -621,6 +621,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
mm->pinned_vm = 0;
memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
spin_lock_init(&mm->page_table_lock);
+ spin_lock_init(&mm->arg_lock);
mm_init_cpumask(mm);
mm_init_aio(mm);
mm_init_owner(mm, p);
diff --git a/kernel/sys.c b/kernel/sys.c
index d5ea3360038c..25cf2aa72d3b 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1854,7 +1854,11 @@ static int prctl_set_mm_map(int opt, const void __user *addr, unsigned long data
return error;
}
- down_write(&mm->mmap_sem);
+ /*
+ * arg_lock protects concurent updates but we still need mmap_sem for
+ * read to exclude races with sys_brk.
+ */
+ down_read(&mm->mmap_sem);
/*
* We don't validate if these members are pointing to
@@ -1868,6 +1872,7 @@ static int prctl_set_mm_map(int opt, const void __user *addr, unsigned long data
* to any problem in kernel itself
*/
+ spin_lock(&mm->arg_lock);
mm->start_code = prctl_map.start_code;
mm->end_code = prctl_map.end_code;
mm->start_data = prctl_map.start_data;
@@ -1879,6 +1884,7 @@ static int prctl_set_mm_map(int opt, const void __user *addr, unsigned long data
mm->arg_end = prctl_map.arg_end;
mm->env_start = prctl_map.env_start;
mm->env_end = prctl_map.env_end;
+ spin_unlock(&mm->arg_lock);
/*
* Note this update of @saved_auxv is lockless thus
@@ -1891,7 +1897,7 @@ static int prctl_set_mm_map(int opt, const void __user *addr, unsigned long data
if (prctl_map.auxv_size)
memcpy(mm->saved_auxv, user_auxv, sizeof(user_auxv));
- up_write(&mm->mmap_sem);
+ up_read(&mm->mmap_sem);
return 0;
}
#endif /* CONFIG_CHECKPOINT_RESTORE */
diff --git a/mm/init-mm.c b/mm/init-mm.c
index 975e49f00f34..02a6962d5b0b 100644
--- a/mm/init-mm.c
+++ b/mm/init-mm.c
@@ -21,6 +21,7 @@ struct mm_struct init_mm = {
.mm_count = ATOMIC_INIT(1),
.mmap_sem = __RWSEM_INITIALIZER(init_mm.mmap_sem),
.page_table_lock = __SPIN_LOCK_UNLOCKED(init_mm.page_table_lock),
+ .arg_lock = __SPIN_LOCK_UNLOCKED(init_mm.arg_lock),
.mmlist = LIST_HEAD_INIT(init_mm.mmlist),
.user_ns = &init_user_ns,
INIT_MM_CONTEXT(init_mm)