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Wed, 31 Jan 2024 15:41:54 +0000 (UTC) Received: from dovecot-director2.suse.de ([10.150.64.162]) by imap2.dmz-prg2.suse.org with ESMTPSA id cPeuHkJqumWyfwAAn2gu4w (envelope-from ); Wed, 31 Jan 2024 15:41:54 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id 0ADF9A0809; Wed, 31 Jan 2024 16:41:54 +0100 (CET) Date: Wed, 31 Jan 2024 16:41:53 +0100 From: Jan Kara To: Edward Adam Davis Cc: syzbot+cdee56dbcdf0096ef605@syzkaller.appspotmail.com, adilger.kernel@dilger.ca, chandan.babu@oracle.com, jack@suse.com, linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, syzkaller-bugs@googlegroups.com, tytso@mit.edu Subject: Re: [PATCH] jbd2: user-memory-access in jbd2__journal_start Message-ID: <20240131154153.domdzkkbqgpkplp2@quack3> References: <000000000000d6e06d06102ae80b@google.com> Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Authentication-Results: smtp-out2.suse.de; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=eAYRS6JE; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=JEcCUXZl X-Spamd-Result: default: False [1.69 / 50.00]; RCVD_VIA_SMTP_AUTH(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_COUNT_THREE(0.00)[3]; DKIM_TRACE(0.00)[suse.cz:+]; MX_GOOD(-0.01)[]; RCPT_COUNT_SEVEN(0.00)[11]; FREEMAIL_TO(0.00)[qq.com]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; R_DKIM_ALLOW(-0.20)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; FREEMAIL_ENVRCPT(0.00)[qq.com]; TO_MATCH_ENVRCPT_ALL(0.00)[]; TAGGED_RCPT(0.00)[cdee56dbcdf0096ef605]; MIME_GOOD(-0.10)[text/plain]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.com:email,suse.cz:dkim]; FUZZY_BLOCKED(0.00)[rspamd.com]; MID_RHS_NOT_FQDN(0.50)[]; RCVD_TLS_ALL(0.00)[]; SUSPICIOUS_RECIPS(1.50)[] X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spam-Score: 1.69 X-Rspamd-Queue-Id: 99A931F747 X-Spam-Level: * X-Spam-Flag: NO X-Spamd-Bar: + On Wed 31-01-24 20:04:27, Edward Adam Davis wrote: > Before reusing the handle, it is necessary to confirm that the transaction is > ready. > > Reported-and-tested-by: syzbot+cdee56dbcdf0096ef605@syzkaller.appspotmail.com > Signed-off-by: Edward Adam Davis Sorry but no. Dave found a way to fix this particular problem in XFS and your patch would not really improve anything because we'd just crash when dereferencing handle->saved_alloc_context. Honza > diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c > index cb0b8d6fc0c6..702312cd5392 100644 > --- a/fs/jbd2/transaction.c > +++ b/fs/jbd2/transaction.c > @@ -493,6 +493,9 @@ handle_t *jbd2__journal_start(journal_t *journal, int nblocks, int rsv_blocks, > return ERR_PTR(-EROFS); > > if (handle) { > + if (handle->saved_alloc_context & ~PF_MEMALLOC_NOFS) > + return ERR_PTR(-EBUSY); > + > J_ASSERT(handle->h_transaction->t_journal == journal); > handle->h_ref++; > return handle; > -- > 2.43.0 > -- Jan Kara SUSE Labs, CR