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Thu, 1 Aug 2024 15:30:42 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id apxoJCKqq2bJFQAAD6G6ig (envelope-from ); Thu, 01 Aug 2024 15:30:42 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id 1B153A08CB; Thu, 1 Aug 2024 17:30:42 +0200 (CEST) Date: Thu, 1 Aug 2024 17:30:42 +0200 From: Jan Kara To: Lizhi Xu Cc: viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, phillip@squashfs.org.uk, squashfs-devel@lists.sourceforge.net, syzbot+24ac24ff58dc5b0d26b9@syzkaller.appspotmail.com, syzkaller-bugs@googlegroups.com Subject: Re: [PATCH V2] squashfs: Add length check in squashfs_symlink_read_folio Message-ID: <20240801153042.prhbovbuys4zmprv@quack3> References: <20240801124220.GP5334@ZenIV> <20240801151740.339272-1-lizhi.xu@windriver.com> Precedence: bulk X-Mailing-List: linux-kernel@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: <20240801151740.339272-1-lizhi.xu@windriver.com> X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Rspamd-Action: no action X-Rspamd-Queue-Id: B13041FB60 X-Spam-Score: -2.31 X-Spam-Level: X-Spam-Flag: NO X-Spamd-Result: default: False [-2.31 / 50.00]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; MID_RHS_NOT_FQDN(0.50)[]; R_DKIM_ALLOW(-0.20)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; TAGGED_RCPT(0.00)[24ac24ff58dc5b0d26b9]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; DNSWL_BLOCKED(0.00)[2a07:de40:b281:106:10:150:64:167:received]; MIME_TRACE(0.00)[0:+]; MISSING_XM_UA(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.com:email,suse.cz:dkim]; RCVD_COUNT_THREE(0.00)[3]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_SEVEN(0.00)[10]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; RCVD_TLS_LAST(0.00)[]; TO_DN_SOME(0.00)[]; DKIM_TRACE(0.00)[suse.cz:+] On Thu 01-08-24 23:17:40, Lizhi Xu wrote: > syzbot report KMSAN: uninit-value in pick_link, the root cause is that > squashfs_symlink_read_folio did not check the length, resulting in folio > not being initialized and did not return the corresponding error code. > > The incorrect value of length is due to the incorrect value of inode->i_size. > > Reported-and-tested-by: syzbot+24ac24ff58dc5b0d26b9@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=24ac24ff58dc5b0d26b9 > Signed-off-by: Lizhi Xu > --- > fs/squashfs/symlink.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/fs/squashfs/symlink.c b/fs/squashfs/symlink.c > index 6ef735bd841a..d5fa5165ddd6 100644 > --- a/fs/squashfs/symlink.c > +++ b/fs/squashfs/symlink.c > @@ -61,6 +61,12 @@ static int squashfs_symlink_read_folio(struct file *file, struct folio *folio) > } > } > > + if (length < 0) { OK, so this would mean that (int)inode->i_size is a negative number. Possible. Perhaps we should rather better validate i_size of symlinks in squashfs_read_inode()? Otherwise it would be a whack-a-mole game of catching places that get confused by bogus i_size... Honza > + ERROR("Unable to read symlink, wrong length [%d]\n", length); > + error = -EINVAL; > + goto out; > + } > + > /* > * Read length bytes from symlink metadata. Squashfs_read_metadata > * is not used here because it can sleep and we want to use > -- > 2.43.0 > -- Jan Kara SUSE Labs, CR