The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x a44be64bbecb15a452496f60db6eacfee2b59c79 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2023051551-gigabyte-tabby-21cd@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

a44be64bbecb ("ext4: don't clear SB_RDONLY when remounting r/w until quota is re-enabled") 3b50d5018ed0 ("ext4: reflect error codes from ext4_multi_mount_protect() to its callers") 3bbef91bdd21 ("ext4: remove an unused variable warning with CONFIG_QUOTA=n")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From a44be64bbecb15a452496f60db6eacfee2b59c79 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o tytso@mit.edu Date: Fri, 5 May 2023 21:02:30 -0400 Subject: [PATCH] ext4: don't clear SB_RDONLY when remounting r/w until quota is re-enabled

When a file system currently mounted read/only is remounted read/write, if we clear the SB_RDONLY flag too early, before the quota is initialized, and there is another process/thread constantly attempting to create a directory, it's possible to trigger the

WARN_ON_ONCE(dquot_initialize_needed(inode));

in ext4_xattr_block_set(), with the following stack trace:

WARNING: CPU: 0 PID: 5338 at fs/ext4/xattr.c:2141 ext4_xattr_block_set+0x2ef2/0x3680 RIP: 0010:ext4_xattr_block_set+0x2ef2/0x3680 fs/ext4/xattr.c:2141 Call Trace: ext4_xattr_set_handle+0xcd4/0x15c0 fs/ext4/xattr.c:2458 ext4_initxattrs+0xa3/0x110 fs/ext4/xattr_security.c:44 security_inode_init_security+0x2df/0x3f0 security/security.c:1147 __ext4_new_inode+0x347e/0x43d0 fs/ext4/ialloc.c:1324 ext4_mkdir+0x425/0xce0 fs/ext4/namei.c:2992 vfs_mkdir+0x29d/0x450 fs/namei.c:4038 do_mkdirat+0x264/0x520 fs/namei.c:4061 __do_sys_mkdirat fs/namei.c:4076 [inline] __se_sys_mkdirat fs/namei.c:4074 [inline] __x64_sys_mkdirat+0x89/0xa0 fs/namei.c:4074

Cc: stable@kernel.org Link: https://lore.kernel.org/r/20230506142419.984260-1-tytso@mit.edu Reported-by: syzbot+6385d7d3065524c5ca6d@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?id=6513f6cb5cd6b5fc9f37e3bb70d273b94be9c34... Signed-off-by: Theodore Ts'o tytso@mit.edu

diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 425b95a7a0ab..c7bc4a2709cc 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -6387,6 +6387,7 @@ static int __ext4_remount(struct fs_context *fc, struct super_block *sb) struct ext4_mount_options old_opts; ext4_group_t g; int err = 0; + int enable_rw = 0; #ifdef CONFIG_QUOTA int enable_quota = 0; int i, j; @@ -6573,7 +6574,7 @@ static int __ext4_remount(struct fs_context *fc, struct super_block *sb) if (err) goto restore_opts;

- sb->s_flags &= ~SB_RDONLY; + enable_rw = 1; if (ext4_has_feature_mmp(sb)) { err = ext4_multi_mount_protect(sb, le64_to_cpu(es->s_mmp_block)); @@ -6632,6 +6633,9 @@ static int __ext4_remount(struct fs_context *fc, struct super_block *sb) if (!test_opt(sb, BLOCK_VALIDITY) && sbi->s_system_blks) ext4_release_system_zone(sb);

+ if (enable_rw) + sb->s_flags &= ~SB_RDONLY; + if (!ext4_has_feature_mmp(sb) || sb_rdonly(sb)) ext4_stop_mmpd(sbi);