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Fri, 27 Mar 2026 19:20:25 -0700 (PDT) Received: from tradnomic.core ([2600:1700:6e30:be0:5717:921b:e9c1:e2a7]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-650092059edsm421403d50.3.2026.03.27.19.20.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 27 Mar 2026 19:20:24 -0700 (PDT) Date: Fri, 27 Mar 2026 19:20:23 -0700 From: Rafael Alejandro Diaz Cruz To: linux-kernel@vger.kernel.org, skhan@linuxfoundation.org, syzkaller-bugs@googlegroups.com Subject: [syzbot] [jfs?] [fat?] general protection fault in txEnd Message-ID: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="xH6SlSvmVBm4Uk5B" Content-Disposition: inline --xH6SlSvmVBm4Uk5B Content-Type: text/plain; charset=us-ascii Content-Disposition: inline #syz test --xH6SlSvmVBm4Uk5B Content-Type: text/x-diff; charset=us-ascii Content-Disposition: attachment; filename="0001-jfs-prevent-null-log-deference-from-superblock-durin.patch" >From b530db0e1844ca2b8fecf527dd5d5457e329adf0 Mon Sep 17 00:00:00 2001 From: rafad900 <19312533+rafad900@users.noreply.github.com> Date: Fri, 27 Mar 2026 18:58:45 -0700 Subject: [PATCH] jfs: prevent null log deference from superblock during read only mode Its not possible to use jfs_create() while the file system is in read only mode. However, there is not a way for jfs_create() to handle this case when txBegin fails. So jfs_create() continues to with the changes to the filesystem and tries to txCommit() them, but when trying to write the changes to the ->log of the superblock, we reach an error telling us that system cannot write and enters panic. Signed-off-by: rafad900 <19312533+rafad900@users.noreply.github.com> --- fs/jfs/namei.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/fs/jfs/namei.c b/fs/jfs/namei.c index 60c4a0e0fca5..25b303276b82 100644 --- a/fs/jfs/namei.c +++ b/fs/jfs/namei.c @@ -97,6 +97,10 @@ static int jfs_create(struct mnt_idmap *idmap, struct inode *dip, } tid = txBegin(dip->i_sb, 0); + if (tid == 0) { + jfs_err("jfs_create: unable to create tblk due to read only filesystem"); + return -EROFS; + } mutex_lock_nested(&JFS_IP(dip)->commit_mutex, COMMIT_MUTEX_PARENT); mutex_lock_nested(&JFS_IP(ip)->commit_mutex, COMMIT_MUTEX_CHILD); -- 2.43.0 --xH6SlSvmVBm4Uk5B--