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Subject[PATCH] AFS: Stop readlink() on AFS crashing because file not passed to afs_readpage()
Date
kAFS crashes when asked to read a symbolic link because page_getlink() passes a
NULL file pointer to read_mapping_page(), but afs_readpage() expects a file
pointer from which to extract a key.

Modify afs_readpage() to request the appropriate key from the calling process's
keyrings if a file struct is not supplied with one attached.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Anton Blanchard <anton@samba.org>
---

fs/afs/file.c | 18 +++++++++++++++---
1 files changed, 15 insertions(+), 3 deletions(-)


diff --git a/fs/afs/file.c b/fs/afs/file.c
index 0149dab..681c2a7 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -134,9 +134,16 @@ static int afs_readpage(struct file *file, struct page *page)

inode = page->mapping->host;

- ASSERT(file != NULL);
- key = file->private_data;
- ASSERT(key != NULL);
+ if (file) {
+ key = file->private_data;
+ ASSERT(key != NULL);
+ } else {
+ key = afs_request_key(AFS_FS_S(inode->i_sb)->volume->cell);
+ if (IS_ERR(key)) {
+ ret = PTR_ERR(key);
+ goto error_nokey;
+ }
+ }

_enter("{%x},{%lu},{%lu}", key_serial(key), inode->i_ino, page->index);

@@ -207,12 +214,17 @@ static int afs_readpage(struct file *file, struct page *page)
unlock_page(page);
}

+ if (!file)
+ key_put(key);
_leave(" = 0");
return 0;

error:
SetPageError(page);
unlock_page(page);
+ if (!file)
+ key_put(key);
+error_nokey:
_leave(" = %d", ret);
return ret;
}


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