Commit-ID: 45e0a79a82d31ddfa4c7c1dd9751ca48406f2fa4
Gitweb: http://git.kernel.org/tip/45e0a79a82d31ddfa4c7c1dd9751ca48406f2fa4
Author: Oleg Nesterov <oleg@xxxxxxxxxx>
AuthorDate: Mon, 19 May 2014 16:13:34 +0200
Committer: Oleg Nesterov <oleg@xxxxxxxxxx>
CommitDate: Mon, 2 Jun 2014 15:54:46 +0200
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: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Suggested-by: Hugh Dickins <hughd@xxxxxxxxxx>
Acked-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
---
kernel/events/uprobes.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index c56b13e..6bfb671 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -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().
*/
- page = read_mapping_page(mapping, offset >> PAGE_CACHE_SHIFT, filp);
+ 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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