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([79.140.150.179]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a9e564c4d2bsm450358166b.70.2024.11.03.10.33.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 03 Nov 2024 10:33:49 -0800 (PST) Message-ID: <6727c20d.170a0220.292362.d5e3@mx.google.com> X-Google-Original-Message-ID: Date: Sat, 2 Nov 2024 17:37:06 +0100 From: Andrew Kanner To: syzbot Cc: linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [ocfs2?] general protection fault in [v2] ocfs2_xa_block_wipe_namevalue References: <67215651.a70a0220.31b018.c8d7@mx.google.com> <67215ae3.050a0220.24951d.0078.GAE@google.com> 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="PAhjboQ2frufRKAg" Content-Disposition: inline In-Reply-To: <67215ae3.050a0220.24951d.0078.GAE@google.com> --PAhjboQ2frufRKAg Content-Type: text/plain; charset=us-ascii Content-Disposition: inline #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master --PAhjboQ2frufRKAg Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename*0="v2-0001-ocfs2-remove-entry-once-instead-of-null-ptr-derefere."; filename*1=patch >From 8a9998952cc5d493cbb6ae9e6187347787b88694 Mon Sep 17 00:00:00 2001 From: Andrew Kanner Date: Tue, 29 Oct 2024 21:26:30 +0100 Subject: [PATCH] ocfs2: remove entry once instead of null-ptr-dereference in ocfs2_xa_remove() Syzkaller is able to provoke null-ptr-dereference in ocfs2_xa_remove(): [ 57.319872] (a.out,1161,7):ocfs2_xa_remove:2028 ERROR: status = -12 [ 57.320420] (a.out,1161,7):ocfs2_xa_cleanup_value_truncate:1999 ERROR: Partial truncate while removing xattr overlay.upper. Leaking 1 clusters and removing the entry [ 57.321727] BUG: kernel NULL pointer dereference, address: 0000000000000004 [...] [ 57.325727] RIP: 0010:ocfs2_xa_block_wipe_namevalue+0x2a/0xc0 [...] [ 57.331328] Call Trace: [ 57.331477] [...] [ 57.333511] ? do_user_addr_fault+0x3e5/0x740 [ 57.333778] ? exc_page_fault+0x70/0x170 [ 57.334016] ? asm_exc_page_fault+0x2b/0x30 [ 57.334263] ? __pfx_ocfs2_xa_block_wipe_namevalue+0x10/0x10 [ 57.334596] ? ocfs2_xa_block_wipe_namevalue+0x2a/0xc0 [ 57.334913] ocfs2_xa_remove_entry+0x23/0xc0 [ 57.335164] ocfs2_xa_set+0x704/0xcf0 [ 57.335381] ? _raw_spin_unlock+0x1a/0x40 [ 57.335620] ? ocfs2_inode_cache_unlock+0x16/0x20 [ 57.335915] ? trace_preempt_on+0x1e/0x70 [ 57.336153] ? start_this_handle+0x16c/0x500 [ 57.336410] ? preempt_count_sub+0x50/0x80 [ 57.336656] ? _raw_read_unlock+0x20/0x40 [ 57.336906] ? start_this_handle+0x16c/0x500 [ 57.337162] ocfs2_xattr_block_set+0xa6/0x1e0 [ 57.337424] __ocfs2_xattr_set_handle+0x1fd/0x5d0 [ 57.337706] ? ocfs2_start_trans+0x13d/0x290 [ 57.337971] ocfs2_xattr_set+0xb13/0xfb0 [ 57.338207] ? dput+0x46/0x1c0 [ 57.338393] ocfs2_xattr_trusted_set+0x28/0x30 [ 57.338665] ? ocfs2_xattr_trusted_set+0x28/0x30 [ 57.338948] __vfs_removexattr+0x92/0xc0 [ 57.339182] __vfs_removexattr_locked+0xd5/0x190 [ 57.339456] ? preempt_count_sub+0x50/0x80 [ 57.339705] vfs_removexattr+0x5f/0x100 [...] Reproducer uses faultinject facility to fail ocfs2_xa_remove() -> ocfs2_xa_value_truncate() with -ENOMEM. In this case the comment mentions that we can return 0 if ocfs2_xa_cleanup_value_truncate() is going to wipe the entry anyway. But the following 'rc' check is wrong and execution flow do 'ocfs2_xa_remove_entry(loc);' twice: * 1st: in ocfs2_xa_cleanup_value_truncate(); * 2nd: returning back to ocfs2_xa_remove() instead of going to 'out'. Fix this by skipping the 2nd removal of the same entry and making syzkaller repro happy. Cc: stable@vger.kernel.org Fixes: 399ff3a748cf ("ocfs2: Handle errors while setting external xattr values.") Reported-by: syzbot+386ce9e60fa1b18aac5b@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/671e13ab.050a0220.2b8c0f.01d0.GAE@google.com/T/ Tested-by: syzbot+386ce9e60fa1b18aac5b@syzkaller.appspotmail.com Signed-off-by: Andrew Kanner --- Notes (akanner): v2: remove rc check completely, suggested by Joseph Qi v1: https://lore.kernel.org/all/20241029224304.2169092-2-andrew.kanner@gmail.com/T/ fs/ocfs2/xattr.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c index dd0a05365e79..73a6f6fd8a8e 100644 --- a/fs/ocfs2/xattr.c +++ b/fs/ocfs2/xattr.c @@ -2036,8 +2036,7 @@ static int ocfs2_xa_remove(struct ocfs2_xa_loc *loc, rc = 0; ocfs2_xa_cleanup_value_truncate(loc, "removing", orig_clusters); - if (rc) - goto out; + goto out; } } -- 2.43.5 --PAhjboQ2frufRKAg--