Commit 45e0a79a authored by Oleg Nesterov's avatar Oleg Nesterov
Browse files

uprobes: Teach copy_insn() to support tmpfs 



tmpfs is widely used but as Denys reports shmem_aops doesn't have
->readpage() and thus you can't probe a binary on this filesystem.

As Hugh suggested we can use shmem_read_mapping_page() in this case,
just we need to check shmem_mapping() if ->readpage == NULL.

Reported-by: default avatarDenys Vlasenko <dvlasenk@redhat.com>
Suggested-by: default avatarHugh Dickins <hughd@google.com>
Acked-by: default avatarSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
parent 7fa31348

kernel/events/uprobes.c

+10 −5
Original line number Diff line number Diff line
@@ -36,6 +36,7 @@ 
#include "../../mm/internal.h"	/* munlock_vma_page */

#include <linux/percpu-rwsem.h>

#include <linux/task_work.h>

#include <linux/shmem_fs.h>



#include <linux/uprobes.h>
@@ -537,10 +538,14 @@ static int __copy_insn(struct address_space *mapping, struct file *filp, 
{

	struct page *page;

	/*

	 * Ensure that the page that has the original instruction is

	 * populated and in page-cache.

	 * Ensure that the page that has the original instruction is populated

	 * and in page-cache. If ->readpage == NULL it must be shmem_mapping(),

	 * see uprobe_register().

	 */

	if (mapping->a_ops->readpage)

		page = read_mapping_page(mapping, offset >> PAGE_CACHE_SHIFT, filp);

	else

		page = shmem_read_mapping_page(mapping, offset >> PAGE_CACHE_SHIFT);

	if (IS_ERR(page))

		return PTR_ERR(page);
@@ -876,8 +881,8 @@ int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer * 
	if (!uc->handler && !uc->ret_handler)

		return -EINVAL;



	/* copy_insn()->read_mapping_page() needs ->readpage() */

	if (!inode->i_mapping->a_ops->readpage)

	/* copy_insn() uses read_mapping_page() or shmem_read_mapping_page() */

	if (!inode->i_mapping->a_ops->readpage && !shmem_mapping(inode->i_mapping))

		return -EIO;

	/* Racy, just to catch the obvious mistakes */

	if (offset > i_size_read(inode))

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