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uprobes: Teach copy_insn() to support tmpfs

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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@redhat.com>
Suggested-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140519184136.GB6750@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Oleg Nesterov 2014-05-19 20:41:36 +02:00 committed by Ingo Molnar
parent 41ccba029e
commit 40814f6805
1 changed files with 10 additions and 5 deletions
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15
kernel/events/uprobes.c
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@ -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))