2.6.30-stable review patch. If anyone has any objections, please let us know. ------------------ From: Oleg Nesterov commit 00f89d218523b9bf6b522349c039d5ac80aa536d upstream. mm_for_maps() takes ->mmap_sem after security checks, this looks strange and obfuscates the locking rules. Move this lock to its single caller, m_start(). Signed-off-by: Oleg Nesterov Acked-by: Serge Hallyn Signed-off-by: James Morris Signed-off-by: Greg Kroah-Hartman --- fs/proc/base.c | 8 +++----- fs/proc/task_mmu.c | 1 + fs/proc/task_nommu.c | 1 + 3 files changed, 5 insertions(+), 5 deletions(-) --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -235,9 +235,8 @@ static int check_mem_permission(struct t struct mm_struct *mm_for_maps(struct task_struct *task) { struct mm_struct *mm = get_task_mm(task); - if (!mm) - return NULL; - if (mm != current->mm) { + + if (mm && mm != current->mm) { /* * task->mm can be changed before security check, * in that case we must notice the change after. @@ -245,10 +244,9 @@ struct mm_struct *mm_for_maps(struct tas if (!ptrace_may_access(task, PTRACE_MODE_READ) || mm != task->mm) { mmput(mm); - return NULL; + mm = NULL; } } - down_read(&mm->mmap_sem); return mm; } --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -119,6 +119,7 @@ static void *m_start(struct seq_file *m, mm = mm_for_maps(priv->task); if (!mm) return NULL; + down_read(&mm->mmap_sem); tail_vma = get_gate_vma(priv->task); priv->tail_vma = tail_vma; --- a/fs/proc/task_nommu.c +++ b/fs/proc/task_nommu.c @@ -189,6 +189,7 @@ static void *m_start(struct seq_file *m, priv->task = NULL; return NULL; } + down_read(&mm->mmap_sem); /* start from the Nth VMA */ for (p = rb_first(&mm->mm_rb); p; p = rb_next(p)) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/