This is a note to let you know that I've just added the patch titled
netfs: Fix netfs_page_mkwrite() to check folio->mapping is valid
to the 6.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
netfs-fix-netfs_page_mkwrite-to-check-folio-mapping-.patch
and it can be found in the queue-6.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 395a2e93407160e835a34dd040cb2e8fcf569814
Author: David Howells <dhowells@xxxxxxxxxx>
Date: Tue Jun 25 13:29:06 2024 +0100
netfs: Fix netfs_page_mkwrite() to check folio->mapping is valid
[ 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@xxxxxxxxxx>
Link: https://lore.kernel.org/r/780211.1719318546@xxxxxxxxxxxxxxxxxxxxxx
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
cc: Jeff Layton <jlayton@xxxxxxxxxx>
cc: netfs@xxxxxxxxxxxxxxx
cc: v9fs@xxxxxxxxxxxxxxx
cc: linux-afs@xxxxxxxxxxxxxxxxxxx
cc: linux-cifs@xxxxxxxxxxxxxxx
cc: linux-mm@xxxxxxxxx
cc: linux-fsdevel@xxxxxxxxxxxxxxx
Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
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) {
