From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1AE7F29AB1A; Fri, 7 Aug 2026 15:32:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786116770; cv=none; b=CoTaEOK7FSaL98jiuVeNkRXOkDimPPfs7uzQg9UHhZQWo7rZFheF8vEv51W83s21o3OhlHbboenvO/oYS4a2jCSF5MkZn+DFw2bIbNef4YhHWVmckMx3qNG4a8zeWT57byXvbJYgR4U80C5KPI7CIFrO6ywwPyO7Krgq+XYDmsE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786116770; c=relaxed/simple; bh=YkdNIRD5690Ub9dR87hBUjqdIZ9kBp9PlpJN+mJ78/E=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=mE1n13MpxlIXWwWua7RqtQ/ghYj1zlzZQjpCV06rOMHWzt5cAJisSBI3m7t2e9KACcqKO4lhjoyaziNjXnZqquooEeR1zI/CBPVQUh/4mt+FEInbol2hqobqZxVVXfkIVD+MNveUMO1cVDdQCGWsrjUPedhlDE/vuEuNQQSlIlA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=mIlG2hea; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="mIlG2hea" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 75BC41F00A3D; Fri, 7 Aug 2026 15:32:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1786116769; bh=ZV0pM1jImc3gMgstgGF9KSoH7AoYPg2iE5M9VTkCXds=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=mIlG2heamqHVvVpjtGDt5kz/GitlmBPZC3ZFdpYDKELHjYjs3rhDEm1IQr+aBGlMM 9DD/o9JGmE6/1q0bHkrQxX3kp7aMvhA+dX2KCC47tsN20tLEVMwdn8XF+BfuaITzmn JyM15ApONbhOAVTjdnJyTLIDq46N9T2mRrzsPXGo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Hongbo Li , Gao Xiang , Sasha Levin Subject: [PATCH 7.1 085/438] erofs: ensure valid f_path for page cache sharing Date: Fri, 7 Aug 2026 16:34:41 +0200 Message-ID: <20260807143429.794853858@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260807143428.008222056@linuxfoundation.org> References: <20260807143428.008222056@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Gao Xiang [ Upstream commit 96b2dbbe58a1ea5df8d29c2fe24b5f04715f4443 ] Previously, backing files for page cache sharing were set up with f_path left as NULL (only f_inode was valid). It worked, but a recent mincore fix relies on f_path.mnt and crashes (found by "erofs/028" on 7.2-rc4): BUG: kernel NULL pointer dereference, address: 0000000000000018 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: Oops: 0000 [#1] SMP PTI CPU: 3 UID: 0 PID: 675528 Comm: fincore Not tainted 7.2.0-rc4-00002-g[]-dirty #1 PREEMPT(lazy) Hardware name: Red Hat KVM, BIOS 1.16.0-4.al8 04/01/2014 RIP: 0010:__do_sys_mincore+0xc0/0x2c0 ... Specify valid paths using valid disconnected dentries together with erofs_ishare_mnt instead of leaving f_path empty, so they are more like real backing files in a pseudo filesystem and standard backing_file_open() can be used directly. Fixes: e187bc02f8fa ("mm: do file ownership checks with the proper mount idmap") Acked-by: Hongbo Li Signed-off-by: Gao Xiang Signed-off-by: Sasha Levin --- fs/erofs/Kconfig | 1 + fs/erofs/internal.h | 4 ++-- fs/erofs/ishare.c | 58 ++++++++++++++++++++++----------------------- 3 files changed, 31 insertions(+), 32 deletions(-) diff --git a/fs/erofs/Kconfig b/fs/erofs/Kconfig index 4789b1077d8ce..1feb28cfe557d 100644 --- a/fs/erofs/Kconfig +++ b/fs/erofs/Kconfig @@ -189,6 +189,7 @@ config EROFS_FS_PCPU_KTHREAD_HIPRI config EROFS_FS_PAGE_CACHE_SHARE bool "EROFS page cache share support (experimental)" depends on EROFS_FS && EROFS_FS_XATTR + select FS_STACK help This enables page cache sharing among inodes with identical content fingerprints on the same machine. diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h index 580f8d9f14e7f..57bd21859c65d 100644 --- a/fs/erofs/internal.h +++ b/fs/erofs/internal.h @@ -288,8 +288,8 @@ struct erofs_inode { struct erofs_inode_fingerprint fingerprint; spinlock_t ishare_lock; }; - /* for each real inode */ - struct inode *sharedinode; + /* for each real filesystem inode */ + struct dentry *sharedentry; }; #endif /* the corresponding vfs inode */ diff --git a/fs/erofs/ishare.c b/fs/erofs/ishare.c index 0868c12fc15b4..25558df98a389 100644 --- a/fs/erofs/ishare.c +++ b/fs/erofs/ishare.c @@ -2,14 +2,13 @@ /* * Copyright (C) 2024, Alibaba Cloud */ +#include #include #include #include #include "internal.h" #include "xattr.h" -#include "../internal.h" - static struct vfsmount *erofs_ishare_mnt; static inline bool erofs_is_ishare_inode(struct inode *inode) @@ -39,10 +38,12 @@ static int erofs_ishare_iget5_set(struct inode *inode, void *data) bool erofs_ishare_fill_inode(struct inode *inode) { + static const struct file_operations empty_fops = {}; struct erofs_sb_info *sbi = EROFS_SB(inode->i_sb); const struct address_space_operations *aops; struct erofs_inode *vi = EROFS_I(inode); struct erofs_inode_fingerprint fp; + struct dentry *sd; struct inode *si; aops = erofs_get_aops(inode); @@ -55,7 +56,9 @@ bool erofs_ishare_fill_inode(struct inode *inode) xxh32(fp.opaque, fp.size, 0), erofs_ishare_iget5_eq, erofs_ishare_iget5_set, &fp); if (si && (inode_state_read_once(si) & I_NEW)) { + si->i_fop = &empty_fops; si->i_mapping->a_ops = aops; + si->i_mode = 0444 | S_IFREG; si->i_size = inode->i_size; unlock_new_inode(si); } else { @@ -71,7 +74,10 @@ bool erofs_ishare_fill_inode(struct inode *inode) return false; } } - vi->sharedinode = si; + sd = d_obtain_alias(si); /* disconnected denties for sharedinodes */ + if (IS_ERR(sd)) + return false; + vi->sharedentry = sd; INIT_LIST_HEAD(&vi->ishare_list); spin_lock(&EROFS_I(si)->ishare_lock); list_add(&vi->ishare_list, &EROFS_I(si)->ishare_list); @@ -81,48 +87,40 @@ bool erofs_ishare_fill_inode(struct inode *inode) void erofs_ishare_free_inode(struct inode *inode) { - struct erofs_inode *vi = EROFS_I(inode); - struct inode *sharedinode = vi->sharedinode; + struct erofs_inode *vi = EROFS_I(inode), *svi; - if (!sharedinode) + if (!vi->sharedentry) return; - spin_lock(&EROFS_I(sharedinode)->ishare_lock); + svi = EROFS_I(d_inode(vi->sharedentry)); + spin_lock(&svi->ishare_lock); list_del(&vi->ishare_list); - spin_unlock(&EROFS_I(sharedinode)->ishare_lock); - iput(sharedinode); - vi->sharedinode = NULL; + spin_unlock(&svi->ishare_lock); + dput(vi->sharedentry); + vi->sharedentry = NULL; } static int erofs_ishare_file_open(struct inode *inode, struct file *file) { - struct inode *sharedinode = EROFS_I(inode)->sharedinode; - struct file *realfile; + struct path sharedpath = { + .mnt = erofs_ishare_mnt, + .dentry = EROFS_I(inode)->sharedentry, + }; + struct file *rf; if (file->f_flags & O_DIRECT) return -EINVAL; - realfile = alloc_empty_backing_file(O_RDONLY|O_NOATIME, current_cred(), - file); - if (IS_ERR(realfile)) - return PTR_ERR(realfile); - ihold(sharedinode); - realfile->f_op = &erofs_file_fops; - realfile->f_inode = sharedinode; - realfile->f_mapping = sharedinode->i_mapping; - path_get(&file->f_path); - backing_file_set_user_path(realfile, &file->f_path); - - file_ra_state_init(&realfile->f_ra, file->f_mapping); - realfile->private_data = EROFS_I(inode); - file->private_data = realfile; + + rf = backing_file_open(file, file->f_flags | O_NOATIME, + &sharedpath, current_cred()); + if (IS_ERR(rf)) + return PTR_ERR(rf); + file->private_data = rf; return 0; } static int erofs_ishare_file_release(struct inode *inode, struct file *file) { - struct file *realfile = file->private_data; - - iput(realfile->f_inode); - fput(realfile); + fput(file->private_data); file->private_data = NULL; return 0; } -- 2.53.0