pagemap: check permissions and capabilities at open time

[firefly-linux-kernel-4.4.55.git] / fs / proc / task_mmu.c

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 6dee68d013ffa69f1f6c9d49873f17f19eb3874d..07c86f51d225f4d34a41229f0238c974f57098b4 100644 (file)
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -310,7 +310,7 @@ show_map_vma(struct seq_file *m, struct vm_area_struct *vma, int is_pid)
         */
        if (file) {
                seq_pad(m, ' ');
-               seq_path(m, &file->f_path, "\n");
+               seq_file_path(m, file, "\n");
                goto done;
        }
 
@@ -597,6 +597,8 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
                [ilog2(VM_HUGEPAGE)]    = "hg",
                [ilog2(VM_NOHUGEPAGE)]  = "nh",
                [ilog2(VM_MERGEABLE)]   = "mg",
+               [ilog2(VM_UFFD_MISSING)]= "um",
+               [ilog2(VM_UFFD_WP)]     = "uw",
        };
        size_t i;
 
@@ -1227,40 +1229,33 @@ static int pagemap_hugetlb_range(pte_t *pte, unsigned long hmask,
 static ssize_t pagemap_read(struct file *file, char __user *buf,
                            size_t count, loff_t *ppos)
 {
-       struct task_struct *task = get_proc_task(file_inode(file));
-       struct mm_struct *mm;
+       struct mm_struct *mm = file->private_data;
        struct pagemapread pm;
-       int ret = -ESRCH;
        struct mm_walk pagemap_walk = {};
        unsigned long src;
        unsigned long svpfn;
        unsigned long start_vaddr;
        unsigned long end_vaddr;
-       int copied = 0;
+       int ret = 0, copied = 0;
 
-       if (!task)
+       if (!mm || !atomic_inc_not_zero(&mm->mm_users))
                goto out;
 
        ret = -EINVAL;
        /* file position must be aligned */
        if ((*ppos % PM_ENTRY_BYTES) || (count % PM_ENTRY_BYTES))
-               goto out_task;
+               goto out_mm;
 
        ret = 0;
        if (!count)
-               goto out_task;
+               goto out_mm;
 
        pm.v2 = soft_dirty_cleared;
        pm.len = (PAGEMAP_WALK_SIZE >> PAGE_SHIFT);
        pm.buffer = kmalloc(pm.len * PM_ENTRY_BYTES, GFP_TEMPORARY);
        ret = -ENOMEM;
        if (!pm.buffer)
-               goto out_task;
-
-       mm = mm_access(task, PTRACE_MODE_READ);
-       ret = PTR_ERR(mm);
-       if (!mm || IS_ERR(mm))
-               goto out_free;
+               goto out_mm;
 
        pagemap_walk.pmd_entry = pagemap_pte_range;
        pagemap_walk.pte_hole = pagemap_pte_hole;
@@ -1273,10 +1268,10 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
        src = *ppos;
        svpfn = src / PM_ENTRY_BYTES;
        start_vaddr = svpfn << PAGE_SHIFT;
-       end_vaddr = TASK_SIZE_OF(task);
+       end_vaddr = mm->task_size;
 
        /* watch out for wraparound */
-       if (svpfn > TASK_SIZE_OF(task) >> PAGE_SHIFT)
+       if (svpfn > mm->task_size >> PAGE_SHIFT)
                start_vaddr = end_vaddr;
 
        /*
@@ -1303,7 +1298,7 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
                len = min(count, PM_ENTRY_BYTES * pm.pos);
                if (copy_to_user(buf, pm.buffer, len)) {
                        ret = -EFAULT;
-                       goto out_mm;
+                       goto out_free;
                }
                copied += len;
                buf += len;
@@ -1313,24 +1308,38 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
        if (!ret || ret == PM_END_OF_BUFFER)
                ret = copied;
 
-out_mm:
-       mmput(mm);
 out_free:
        kfree(pm.buffer);
-out_task:
-       put_task_struct(task);
+out_mm:
+       mmput(mm);
 out:
        return ret;
 }
 
 static int pagemap_open(struct inode *inode, struct file *file)
 {
+       struct mm_struct *mm;
+
        /* do not disclose physical addresses: attack vector */
        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;
        pr_warn_once("Bits 55-60 of /proc/PID/pagemap entries are about "
                        "to stop being page-shift some time soon. See the "
                        "linux/Documentation/vm/pagemap.txt for details.\n");
+
+       mm = proc_mem_open(inode, PTRACE_MODE_READ);
+       if (IS_ERR(mm))
+               return PTR_ERR(mm);
+       file->private_data = mm;
+       return 0;
+}
+
+static int pagemap_release(struct inode *inode, struct file *file)
+{
+       struct mm_struct *mm = file->private_data;
+
+       if (mm)
+               mmdrop(mm);
        return 0;
 }
 
@@ -1338,6 +1347,7 @@ const struct file_operations proc_pagemap_operations = {
        .llseek         = mem_lseek, /* borrow this */
        .read           = pagemap_read,
        .open           = pagemap_open,
+       .release        = pagemap_release,
 };
 #endif /* CONFIG_PROC_PAGE_MONITOR */
 
@@ -1509,7 +1519,7 @@ static int show_numa_map(struct seq_file *m, void *v, int is_pid)
 
        if (file) {
                seq_puts(m, " file=");
-               seq_path(m, &file->f_path, "\n\t= ");
+               seq_file_path(m, file, "\n\t= ");
        } else if (vma->vm_start <= mm->brk && vma->vm_end >= mm->start_brk) {
                seq_puts(m, " heap");
        } else {