pagemap: fix bug in add_to_pagemap, require aligned-length reads of /proc/pid/pagemap
Thomas Tuttle [Fri, 6 Jun 2008 05:46:31 +0000 (22:46 -0700)]
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>

fs/proc/task_mmu.c

index 88717c0..1740362 100644 (file)
@@ -496,7 +496,7 @@ const struct file_operations proc_clear_refs_operations = {
 };
 
 struct pagemapread {
-       char __user *out, *end;
+       u64 __user *out, *end;
 };
 
 #define PM_ENTRY_BYTES      sizeof(u64)
@@ -519,21 +519,11 @@ 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;
 }
 
@@ -634,7 +624,7 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
 
        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;
@@ -664,8 +654,8 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
                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;
@@ -690,9 +680,9 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
                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: