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authorDavid Howells <dhowells@redhat.com>2020-05-17 21:21:05 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2020-05-18 10:29:17 -0700
commit9d1be4f4dc5ff1c66c86acfd2c35765d9e3776b3 (patch)
tree4551a00806a3ed8822d0d190331124249527d6f7 /fs/afs/fsclient.c
parentb9bbe6ed63b2b9f2c9ee5cbd0f2c946a2723f4ce (diff)
downloadlinux-9d1be4f4dc5ff1c66c86acfd2c35765d9e3776b3.tar.gz
afs: Don't unlock fetched data pages until the op completes successfully
Don't call req->page_done() on each page as we finish filling it with the data coming from the network. Whilst this might speed up the application a bit, it's a problem if there's a network failure and the operation has to be reissued. If this happens, an oops occurs because afs_readpages_page_done() clears the pointer to each page it unlocks and when a retry happens, the pointers to the pages it wants to fill are now NULL (and the pages have been unlocked anyway). Instead, wait till the operation completes successfully and only then release all the pages after clearing any terminal gap (the server can give us less data than we requested as we're allowed to ask for more than is available). KASAN produces a bug like the following, and even without KASAN, it can oops and panic. BUG: KASAN: wild-memory-access in _copy_to_iter+0x323/0x5f4 Write of size 1404 at addr 0005088000000000 by task md5sum/5235 CPU: 0 PID: 5235 Comm: md5sum Not tainted 5.7.0-rc3-fscache+ #250 Hardware name: ASUS All Series/H97-PLUS, BIOS 2306 10/09/2014 Call Trace: memcpy+0x39/0x58 _copy_to_iter+0x323/0x5f4 __skb_datagram_iter+0x89/0x2a6 skb_copy_datagram_iter+0x129/0x135 rxrpc_recvmsg_data.isra.0+0x615/0xd42 rxrpc_kernel_recv_data+0x1e9/0x3ae afs_extract_data+0x139/0x33a yfs_deliver_fs_fetch_data64+0x47a/0x91b afs_deliver_to_call+0x304/0x709 afs_wait_for_call_to_complete+0x1cc/0x4ad yfs_fs_fetch_data+0x279/0x288 afs_fetch_data+0x1e1/0x38d afs_readpages+0x593/0x72e read_pages+0xf5/0x21e __do_page_cache_readahead+0x128/0x23f ondemand_readahead+0x36e/0x37f generic_file_buffered_read+0x234/0x680 new_sync_read+0x109/0x17e vfs_read+0xe6/0x138 ksys_read+0xd8/0x14d do_syscall_64+0x6e/0x8a entry_SYSCALL_64_after_hwframe+0x49/0xb3 Fixes: 196ee9cd2d04 ("afs: Make afs_fs_fetch_data() take a list of pages") Fixes: 30062bd13e36 ("afs: Implement YFS support in the fs client") Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/afs/fsclient.c')
-rw-r--r--fs/afs/fsclient.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/fs/afs/fsclient.c b/fs/afs/fsclient.c
index 68fc46634346..d2b3798c1932 100644
--- a/fs/afs/fsclient.c
+++ b/fs/afs/fsclient.c
@@ -385,8 +385,6 @@ static int afs_deliver_fs_fetch_data(struct afs_call *call)
ASSERTCMP(req->offset, <=, PAGE_SIZE);
if (req->offset == PAGE_SIZE) {
req->offset = 0;
- if (req->page_done)
- req->page_done(req);
req->index++;
if (req->remain > 0)
goto begin_page;
@@ -440,11 +438,13 @@ static int afs_deliver_fs_fetch_data(struct afs_call *call)
if (req->offset < PAGE_SIZE)
zero_user_segment(req->pages[req->index],
req->offset, PAGE_SIZE);
- if (req->page_done)
- req->page_done(req);
req->offset = 0;
}
+ if (req->page_done)
+ for (req->index = 0; req->index < req->nr_pages; req->index++)
+ req->page_done(req);
+
_leave(" = 0 [done]");
return 0;
}