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Commit aae8679b authored by Thomas Tuttle's avatar Thomas Tuttle Committed by Linus Torvalds
Browse files

pagemap: fix bug in add_to_pagemap, require aligned-length reads of /proc/pid/pagemap 



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: default avatarThomas Tuttle <ttuttle@google.com>
Cc: Matt Mackall <mpm@selenic.com>
Cc: <stable@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d1ee2971

fs/proc/task_mmu.c

+9 −19
Original line number Diff line number Diff line
@@ -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: