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authorDavid Howells <dhowells@redhat.com>2023-03-01 01:38:38 +0300
committerSteve French <stfrench@microsoft.com>2023-03-02 03:18:25 +0300
commit71562809e401b2f5ad371d99ce0323e988406fd6 (patch)
treec7b4539b889969a7b8153e1acf15e826ca8401ec /fs
parent1bcd548d935a33c6fc58331405eb1b82fd6150de (diff)
downloadlinux-71562809e401b2f5ad371d99ce0323e988406fd6.tar.xz
cifs: Fix memory leak in direct I/O
When __cifs_readv() and __cifs_writev() extract pages from a user-backed iterator into a BVEC-type iterator, they set ->bv_need_unpin to note whether they need to unpin the pages later. However, in both cases they examine the BVEC-type iterator and not the source iterator - and so bv_need_unpin doesn't get set and the pages are leaked. I think this may be responsible for the generic/208 xfstest failing occasionally with: WARNING: CPU: 0 PID: 3064 at mm/gup.c:218 try_grab_page+0x65/0x100 RIP: 0010:try_grab_page+0x65/0x100 follow_page_pte+0x1a7/0x570 __get_user_pages+0x1a2/0x650 __gup_longterm_locked+0xdc/0xb50 internal_get_user_pages_fast+0x17f/0x310 pin_user_pages_fast+0x46/0x60 iov_iter_extract_pages+0xc9/0x510 ? __kmalloc_large_node+0xb1/0x120 ? __kmalloc_node+0xbe/0x130 netfs_extract_user_iter+0xbf/0x200 [netfs] __cifs_writev+0x150/0x330 [cifs] vfs_write+0x2a8/0x3c0 ksys_pwrite64+0x65/0xa0 with the page refcount going negative. This is less unlikely than it seems because the page is being pinned, not simply got, and so the refcount increased by 1024 each time, and so only needs to be called around ~2097152 for the refcount to go negative. Further, the test program (aio-dio-invalidate-failure) uses a 32MiB static buffer and all the PTEs covering it refer to the same page because it's never written to. The warning in try_grab_page(): if (WARN_ON_ONCE(folio_ref_count(folio) <= 0)) return -ENOMEM; then trips and prevents us ever using the page again for DIO at least. Fixes: d08089f649a0 ("cifs: Change the I/O paths to use an iterator rather than a page list") Reported-by: Murphy Zhou <jencce.kernel@gmail.com> Link: https://lore.kernel.org/r/CAH2r5mvaTsJ---n=265a4zqRA7pP+o4MJ36WCQUS6oPrOij8cw@mail.gmail.com Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Paulo Alcantara (SUSE) <pc@manguebit.com> cc: Shyam Prasad N <nspmangalore@gmail.com> cc: Rohith Surabattula <rohiths.msft@gmail.com> cc: Jeff Layton <jlayton@kernel.org> cc: linux-cifs@vger.kernel.org Signed-off-by: Steve French <stfrench@microsoft.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/cifs/file.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index ec0694a65c7b..4d4a2d82636d 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -3612,7 +3612,7 @@ static ssize_t __cifs_writev(
ctx->nr_pinned_pages = rc;
ctx->bv = (void *)ctx->iter.bvec;
- ctx->bv_need_unpin = iov_iter_extract_will_pin(&ctx->iter);
+ ctx->bv_need_unpin = iov_iter_extract_will_pin(from);
} else if ((iov_iter_is_bvec(from) || iov_iter_is_kvec(from)) &&
!is_sync_kiocb(iocb)) {
/*
@@ -4148,7 +4148,7 @@ static ssize_t __cifs_readv(
ctx->nr_pinned_pages = rc;
ctx->bv = (void *)ctx->iter.bvec;
- ctx->bv_need_unpin = iov_iter_extract_will_pin(&ctx->iter);
+ ctx->bv_need_unpin = iov_iter_extract_will_pin(to);
ctx->should_dirty = true;
} else if ((iov_iter_is_bvec(to) || iov_iter_is_kvec(to)) &&
!is_sync_kiocb(iocb)) {