[patch 43/50] pagemap: fix bug in add_to_pagemap, require aligned-length reads of /proc/pid/pagemap

[Chris Wright]

-stable review patch.  If anyone has any objections, please let us know.
---------------------

From: Thomas Tuttle <ttuttle@xxxxxxxxxx>

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@xxxxxxxxxxxxxxxxxxxx: coding-style fixes]
Signed-off-by: Thomas Tuttle <ttuttle@xxxxxxxxxx>
Cc: Matt Mackall <mpm@xxxxxxxxxxx>
Cc: <stable@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Chris Wright <chrisw@xxxxxxxxxxxx>
---
 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:

-- 
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/