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
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 <firstname.lastname@example.org>
Reviewed-by: Matthew Wilcox (Oracle) <email@example.com>
Signed-off-by: Linus Torvalds <firstname.lastname@example.org>
2 files changed