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Mon, 29 Jul 2024 11:54:23 +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 RdDrD++Cp2bOOAAAD6G6ig (envelope-from ); Mon, 29 Jul 2024 11:54:23 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id CFDB4A099C; Mon, 29 Jul 2024 13:54:18 +0200 (CEST) Date: Mon, 29 Jul 2024 13:54:18 +0200 From: Jan Kara To: Sasha Levin Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, Justin Stitt , linux-hardening@vger.kernel.org, Kees Cook , Jan Kara , Christian Brauner , viro@zeniv.linux.org.uk, nathan@kernel.org, linux-fsdevel@vger.kernel.org, llvm@lists.linux.dev Subject: Re: [PATCH AUTOSEL 6.10 02/16] fs: remove accidental overflow during wraparound check Message-ID: <20240729115418.xzfmanyqtipkuttx@quack3> References: <20240728004739.1698541-1-sashal@kernel.org> <20240728004739.1698541-2-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@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: <20240728004739.1698541-2-sashal@kernel.org> X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Rspamd-Action: no action X-Rspamd-Queue-Id: 5F3941F790 X-Spam-Score: -3.81 X-Spam-Level: X-Spam-Flag: NO X-Spamd-Result: default: False [-3.81 / 50.00]; BAYES_HAM(-3.00)[100.00%]; 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)[]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; MISSING_XM_UA(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; RCPT_COUNT_TWELVE(0.00)[12]; MIME_TRACE(0.00)[0:+]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.com:email,chromium.org:email,suse.cz:email,suse.cz:dkim,imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo]; RCVD_COUNT_THREE(0.00)[3]; TO_DN_SOME(0.00)[]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; 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)[]; DNSWL_BLOCKED(0.00)[2a07:de40:b281:106:10:150:64:167:received]; DKIM_TRACE(0.00)[suse.cz:+] On Sat 27-07-24 20:47:19, Sasha Levin wrote: > From: Justin Stitt > > [ Upstream commit 23cc6ef6fd453b13502caae23130844e7d6ed0fe ] Sasha, this commit is only about silencing false-positive UBSAN warning. Not sure if it is really a stable material... Honza > > Running syzkaller with the newly enabled signed integer overflow > sanitizer produces this report: > > [ 195.401651] ------------[ cut here ]------------ > [ 195.404808] UBSAN: signed-integer-overflow in ../fs/open.c:321:15 > [ 195.408739] 9223372036854775807 + 562984447377399 cannot be represented in type 'loff_t' (aka 'long long') > [ 195.414683] CPU: 1 PID: 703 Comm: syz-executor.0 Not tainted 6.8.0-rc2-00039-g14de58dbe653-dirty #11 > [ 195.420138] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 > [ 195.425804] Call Trace: > [ 195.427360] > [ 195.428791] dump_stack_lvl+0x93/0xd0 > [ 195.431150] handle_overflow+0x171/0x1b0 > [ 195.433640] vfs_fallocate+0x459/0x4f0 > ... > [ 195.490053] ------------[ cut here ]------------ > [ 195.493146] UBSAN: signed-integer-overflow in ../fs/open.c:321:61 > [ 195.497030] 9223372036854775807 + 562984447377399 cannot be represented in type 'loff_t' (aka 'long long) > [ 195.502940] CPU: 1 PID: 703 Comm: syz-executor.0 Not tainted 6.8.0-rc2-00039-g14de58dbe653-dirty #11 > [ 195.508395] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 > [ 195.514075] Call Trace: > [ 195.515636] > [ 195.517000] dump_stack_lvl+0x93/0xd0 > [ 195.519255] handle_overflow+0x171/0x1b0 > [ 195.521677] vfs_fallocate+0x4cb/0x4f0 > [ 195.524033] __x64_sys_fallocate+0xb2/0xf0 > > Historically, the signed integer overflow sanitizer did not work in the > kernel due to its interaction with `-fwrapv` but this has since been > changed [1] in the newest version of Clang. It was re-enabled in the > kernel with Commit 557f8c582a9ba8ab ("ubsan: Reintroduce signed overflow > sanitizer"). > > Let's use the check_add_overflow helper to first verify the addition > stays within the bounds of its type (long long); then we can use that > sum for the following check. > > Link: https://github.com/llvm/llvm-project/pull/82432 [1] > Closes: https://github.com/KSPP/linux/issues/356 > Cc: linux-hardening@vger.kernel.org > Reviewed-by: Kees Cook > Signed-off-by: Justin Stitt > Link: https://lore.kernel.org/r/20240513-b4-sio-vfs_fallocate-v2-1-db415872fb16@google.com > Reviewed-by: Jan Kara > Signed-off-by: Christian Brauner > Signed-off-by: Sasha Levin > --- > fs/open.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/fs/open.c b/fs/open.c > index 278b3edcda444..1dd123ba34ee9 100644 > --- a/fs/open.c > +++ b/fs/open.c > @@ -247,6 +247,7 @@ int vfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len) > { > struct inode *inode = file_inode(file); > long ret; > + loff_t sum; > > if (offset < 0 || len <= 0) > return -EINVAL; > @@ -319,8 +320,11 @@ int vfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len) > if (!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode)) > return -ENODEV; > > - /* Check for wrap through zero too */ > - if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len) < 0)) > + /* Check for wraparound */ > + if (check_add_overflow(offset, len, &sum)) > + return -EFBIG; > + > + if (sum > inode->i_sb->s_maxbytes) > return -EFBIG; > > if (!file->f_op->fallocate) > -- > 2.43.0 > -- Jan Kara SUSE Labs, CR