The patch titled
Subject: pagemap: check permissions and capabilities at open time
has been added to the -mm tree. Its filename is
pagemap-check-permissions-and-capabilities-at-open-time.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/pagemap-check-permissions-and-capabilities-at-open-time.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/pagemap-check-permissions-and-capabilities-at-open-time.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
Subject: pagemap: check permissions and capabilities at open time
This patchset makes pagemap useable again in the safe way (after row
hammer bug it was made CAP_SYS_ADMIN-only). This patchset restores access
for non-privileged users but hides PFNs from them.
Also it adds bit 'map-exclusive' which is set if page is mapped only here:
it helps in estimation of working set without exposing pfns and allows to
distinguish CoWed and non-CoWed private anonymous pages.
Second patch removes page-shift bits and completes migration to the new
pagemap format: flags soft-dirty and mmap-exclusive are available only in
the new format.
This patch (of 5):
This patch moves permission checks from pagemap_read() into pagemap_open().
Pointer to mm is saved in file->private_data. This reference pins only
mm_struct itself. /proc/*/mem, maps, smaps already work in the same way.
See http://lkml.kernel.org/r/CA+55aFyKpWrt_Ajzh1rzp_GcwZ4=6Y=kOv8hBz172CFJp6L8Tg@xxxxxxxxxxxxxx
Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: Mark Williamson <mwilliamson@xxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/task_mmu.c | 48 +++++++++++++++++++++++++------------------
1 file changed, 28 insertions(+), 20 deletions(-)
diff -puN fs/proc/task_mmu.c~pagemap-check-permissions-and-capabilities-at-open-time fs/proc/task_mmu.c
--- a/fs/proc/task_mmu.c~pagemap-check-permissions-and-capabilities-at-open-time
+++ a/fs/proc/task_mmu.c
@@ -1230,40 +1230,33 @@ static int pagemap_hugetlb_range(pte_t *
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;
@@ -1276,10 +1269,10 @@ static ssize_t pagemap_read(struct file
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;
/*
@@ -1306,7 +1299,7 @@ static ssize_t pagemap_read(struct file
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;
@@ -1316,24 +1309,38 @@ static ssize_t pagemap_read(struct file
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;
}
@@ -1341,6 +1348,7 @@ const struct file_operations proc_pagema
.llseek = mem_lseek, /* borrow this */
.read = pagemap_read,
.open = pagemap_open,
+ .release = pagemap_release,
};
#endif /* CONFIG_PROC_PAGE_MONITOR */
_
Patches currently in -mm which might be from khlebnikov@xxxxxxxxxxxxxx are
pagemap-check-permissions-and-capabilities-at-open-time.patch
pagemap-switch-to-the-new-format-and-do-some-cleanup.patch
pagemap-rework-hugetlb-and-thp-report.patch
pagemap-hide-physical-addresses-from-non-privileged-users.patch
pagemap-add-mmap-exclusive-bit-for-marking-pages-mapped-only-here.patch
pagemap-add-mmap-exclusive-bit-for-marking-pages-mapped-only-here-fix.patch
--
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