6.9-stable review patch. If anyone has any objections, please let me know.
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From: David Howells dhowells@redhat.com
[ Upstream commit a81c98bfa40c11f8ea79b5a9b3f5fda73bfbb4d2 ]
Fix netfs_page_mkwrite() to check that folio->mapping is valid once it has taken the folio lock (as filemap_page_mkwrite() does). Without this, generic/247 occasionally oopses with something like the following:
BUG: kernel NULL pointer dereference, address: 0000000000000000 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page
RIP: 0010:trace_event_raw_event_netfs_folio+0x61/0xc0 ... Call Trace: <TASK> ? __die_body+0x1a/0x60 ? page_fault_oops+0x6e/0xa0 ? exc_page_fault+0xc2/0xe0 ? asm_exc_page_fault+0x22/0x30 ? trace_event_raw_event_netfs_folio+0x61/0xc0 trace_netfs_folio+0x39/0x40 netfs_page_mkwrite+0x14c/0x1d0 do_page_mkwrite+0x50/0x90 do_pte_missing+0x184/0x200 __handle_mm_fault+0x42d/0x500 handle_mm_fault+0x121/0x1f0 do_user_addr_fault+0x23e/0x3c0 exc_page_fault+0xc2/0xe0 asm_exc_page_fault+0x22/0x30
This is due to the invalidate_inode_pages2_range() issued at the end of the DIO write interfering with the mmap'd writes.
Fixes: 102a7e2c598c ("netfs: Allow buffered shared-writeable mmap through netfs_page_mkwrite()") Signed-off-by: David Howells dhowells@redhat.com Link: https://lore.kernel.org/r/780211.1719318546@warthog.procyon.org.uk Reviewed-by: Jeff Layton jlayton@kernel.org cc: Matthew Wilcox willy@infradead.org cc: Jeff Layton jlayton@kernel.org cc: netfs@lists.linux.dev cc: v9fs@lists.linux.dev cc: linux-afs@lists.infradead.org cc: linux-cifs@vger.kernel.org cc: linux-mm@kvack.org cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner brauner@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/netfs/buffered_write.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/fs/netfs/buffered_write.c b/fs/netfs/buffered_write.c index 912ad0a1df021..72e4fa233c526 100644 --- a/fs/netfs/buffered_write.c +++ b/fs/netfs/buffered_write.c @@ -507,6 +507,7 @@ vm_fault_t netfs_page_mkwrite(struct vm_fault *vmf, struct netfs_group *netfs_gr { struct folio *folio = page_folio(vmf->page); struct file *file = vmf->vma->vm_file; + struct address_space *mapping = file->f_mapping; struct inode *inode = file_inode(file); vm_fault_t ret = VM_FAULT_RETRY; int err; @@ -520,6 +521,11 @@ vm_fault_t netfs_page_mkwrite(struct vm_fault *vmf, struct netfs_group *netfs_gr
if (folio_lock_killable(folio) < 0) goto out; + if (folio->mapping != mapping) { + folio_unlock(folio); + ret = VM_FAULT_NOPAGE; + goto out; + }
/* Can we see a streaming write here? */ if (WARN_ON(!folio_test_uptodate(folio))) { @@ -529,7 +535,7 @@ vm_fault_t netfs_page_mkwrite(struct vm_fault *vmf, struct netfs_group *netfs_gr
if (netfs_folio_group(folio) != netfs_group) { folio_unlock(folio); - err = filemap_fdatawait_range(inode->i_mapping, + err = filemap_fdatawait_range(mapping, folio_pos(folio), folio_pos(folio) + folio_size(folio)); switch (err) {