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Registered in England and Wales under Company Registration No. 3798903 From: David Howells To: Christian Brauner , Matthew Wilcox cc: dhowells@redhat.com, Jeff Layton , netfs@lists.linux.dev, v9fs@lists.linux.dev, linux-afs@lists.infradead.org, linux-cifs@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] netfs: Fix netfs_page_mkwrite() to check folio->mapping is valid MIME-Version: 1.0 Content-ID: <614256.1719228181.1@warthog.procyon.org.uk> Date: Mon, 24 Jun 2024 12:23:01 +0100 Message-ID: <614257.1719228181@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: D0FEB80022 X-Stat-Signature: p3aiksj8z1x3n8nnwx7ywfeothcrccsk X-HE-Tag: 1719228192-934494 X-HE-Meta: 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 pWNWSmLc 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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: ? __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 cc: Matthew Wilcox cc: Jeff Layton 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 --- fs/netfs/buffered_write.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/fs/netfs/buffered_write.c b/fs/netfs/buffered_write.c index c36643c97cb5..6a6387b3aaff 100644 --- a/fs/netfs/buffered_write.c +++ b/fs/netfs/buffered_write.c @@ -497,6 +497,7 @@ vm_fault_t netfs_page_mkwrite(struct vm_fault *vmf, struct netfs_group *netfs_gr struct netfs_group *group; 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); struct netfs_inode *ictx = netfs_inode(inode); vm_fault_t ret = VM_FAULT_RETRY; @@ -508,6 +509,10 @@ 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) { + ret = VM_FAULT_NOPAGE | VM_FAULT_LOCKED; + goto out; + } if (folio_wait_writeback_killable(folio)) { ret = VM_FAULT_LOCKED; @@ -523,7 +528,7 @@ vm_fault_t netfs_page_mkwrite(struct vm_fault *vmf, struct netfs_group *netfs_gr group = netfs_folio_group(folio); if (group != netfs_group && group != NETFS_FOLIO_COPY_TO_CACHE) { 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) {