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Subject[patch 43/50] pagemap: fix bug in add_to_pagemap, require aligned-length reads of /proc/pid/pagemap
-stable review patch.  If anyone has any objections, please let us know.
---------------------

From: Thomas Tuttle <ttuttle@google.com>

upstream commit: aae8679b0ebcaa92f99c1c3cb0cd651594a43915

Fix a bug in add_to_pagemap. Previously, since pm->out was a char *,
put_user was only copying 1 byte of every PFN, resulting in the top 7
bytes of each PFN not being copied. By requiring that reads be a multiple
of 8 bytes, I can make pm->out and pm->end u64*s instead of char*s, which
makes put_user work properly, and also simplifies the logic in
add_to_pagemap a bit.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Thomas Tuttle <ttuttle@google.com>
Cc: Matt Mackall <mpm@selenic.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
---
fs/proc/task_mmu.c | 28 +++++++++-------------------
1 file changed, 9 insertions(+), 19 deletions(-)

--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -524,7 +524,7 @@ const struct file_operations proc_clear_
};

struct pagemapread {
- char __user *out, *end;
+ u64 __user *out, *end;
};

#define PM_ENTRY_BYTES sizeof(u64)
@@ -547,21 +547,11 @@ struct pagemapread {
static int add_to_pagemap(unsigned long addr, u64 pfn,
struct pagemapread *pm)
{
- /*
- * Make sure there's room in the buffer for an
- * entire entry. Otherwise, only copy part of
- * the pfn.
- */
- if (pm->out + PM_ENTRY_BYTES >= pm->end) {
- if (copy_to_user(pm->out, &pfn, pm->end - pm->out))
- return -EFAULT;
- pm->out = pm->end;
- return PM_END_OF_BUFFER;
- }
-
if (put_user(pfn, pm->out))
return -EFAULT;
- pm->out += PM_ENTRY_BYTES;
+ pm->out++;
+ if (pm->out >= pm->end)
+ return PM_END_OF_BUFFER;
return 0;
}

@@ -662,7 +652,7 @@ static ssize_t pagemap_read(struct file

ret = -EINVAL;
/* file position must be aligned */
- if (*ppos % PM_ENTRY_BYTES)
+ if ((*ppos % PM_ENTRY_BYTES) || (count % PM_ENTRY_BYTES))
goto out_task;

ret = 0;
@@ -692,8 +682,8 @@ static ssize_t pagemap_read(struct file
goto out_pages;
}

- pm.out = buf;
- pm.end = buf + count;
+ pm.out = (u64 *)buf;
+ pm.end = (u64 *)(buf + count);

if (!ptrace_may_attach(task)) {
ret = -EIO;
@@ -718,9 +708,9 @@ static ssize_t pagemap_read(struct file
if (ret == PM_END_OF_BUFFER)
ret = 0;
/* don't need mmap_sem for these, but this looks cleaner */
- *ppos += pm.out - buf;
+ *ppos += (char *)pm.out - buf;
if (!ret)
- ret = pm.out - buf;
+ ret = (char *)pm.out - buf;
}

out_pages:
--


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