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Mon, 22 Jan 2024 16:45:57 -0800 (PST) From: Kees Cook To: linux-hardening@vger.kernel.org Cc: Kees Cook , Steve French , Paulo Alcantara , Ronnie Sahlberg , Shyam Prasad N , Tom Talpey , linux-cifs@vger.kernel.org, samba-technical@lists.samba.org, "Gustavo A. R. Silva" , Bill Wendling , Justin Stitt , linux-kernel@vger.kernel.org Subject: [PATCH 45/82] cifs: Refactor intentional wrap-around test Date: Mon, 22 Jan 2024 16:27:20 -0800 Message-Id: <20240123002814.1396804-45-keescook@chromium.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240122235208.work.748-kees@kernel.org> References: <20240122235208.work.748-kees@kernel.org> Precedence: bulk X-Mailing-List: linux-cifs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2484; i=keescook@chromium.org; h=from:subject; bh=xNoy2DEKxPexmysOm1XEIuiIvV0tGdJOvp+eDp29H/0=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBlrwgIC9jJ8iaLQLpMHm2oaP/gJFWo6z16pwWIH frFA2mk5NyJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCZa8ICAAKCRCJcvTf3G3A JidPD/43jyw+n24wTT1kk3hrH8GaVm1jhQv0Peatn4T8EGaS6EeAlVVxyaPfgjyRlynINUrXvsK HaEtBB4FIngOHcdhwrcU6rjQ6dR1uIlyMg4E72yb8tVbdliP6qwkiT2ecDroeGiBrW1oaJGvoBV +BW2xWnKw/xUWkEuY5/gOAg70JYqLdhrj1+O/sBKrVG3Z//+lHssd0Gua1rN5yLWCexaUbs98/P fUwsGsPV3XXcpZRHQm6gxLzlUxUl2QRmAZpbc6yHf+iQqeQJNvMF+U9LjgVvk+FancFxNeVl71s 1kNlAm/+gBZou1Mk97HK49dTT5BMklB1S9hoNjZWRMtCnuCxRyYOuMS6RpQxRkCQnU0BUBHuE2K h/F4dHaFnL67EdIG87Kkpl9QtRSQWBwr4BNIYF0jfEo/cM19ltK1b6Rs8D4X/OFvNYs0IABel5w znOAKXPr7JmH6UW2Sld9YPHUedVxOCMuk/i9PgzIUxJkF3D3W1yv/A0YaN/j0jNvdSkE3qalwbg QSWUHXbJtPytx7L+XPKl1zACMCU0Ul5NQUl11Vk2NbjuxayThC1Y0A1TayLxVq1gtmBUyO09nsS dH3jGnzw/kZTzoU6P0S5pw7QDLI6CVNv3Hho4jhx+k2DERI0biLRv+dl2VEtnMsVph/T9izC/Va gR1KNJ/P1/j+s7Q== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 In an effort to separate intentional arithmetic wrap-around from unexpected wrap-around, we need to refactor places that depend on this kind of math. One of the most common code patterns of this is: VAR + value < VAR Notably, this is considered "undefined behavior" for signed and pointer types, which the kernel works around by using the -fno-strict-overflow option in the build[1] (which used to just be -fwrapv). Regardless, we want to get the kernel source to the position where we can meaningfully instrument arithmetic wrap-around conditions and catch them when they are unexpected, regardless of whether they are signed[2], unsigned[3], or pointer[4] types. Refactor open-coded wrap-around addition test to use add_would_overflow(). This paves the way to enabling the wrap-around sanitizers in the future. Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1] Link: https://github.com/KSPP/linux/issues/26 [2] Link: https://github.com/KSPP/linux/issues/27 [3] Link: https://github.com/KSPP/linux/issues/344 [4] Cc: Steve French Cc: Paulo Alcantara Cc: Ronnie Sahlberg Cc: Shyam Prasad N Cc: Tom Talpey Cc: linux-cifs@vger.kernel.org Cc: samba-technical@lists.samba.org Signed-off-by: Kees Cook --- fs/smb/client/smb2pdu.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/smb/client/smb2pdu.c b/fs/smb/client/smb2pdu.c index 288199f0b987..85399525f0a7 100644 --- a/fs/smb/client/smb2pdu.c +++ b/fs/smb/client/smb2pdu.c @@ -5007,7 +5007,7 @@ num_entries(int infotype, char *bufstart, char *end_of_buf, char **lastentry, entryptr = bufstart; while (1) { - if (entryptr + next_offset < entryptr || + if (add_would_overflow(entryptr, next_offset) || entryptr + next_offset > end_of_buf || entryptr + next_offset + size > end_of_buf) { cifs_dbg(VFS, "malformed search entry would overflow\n"); @@ -5023,7 +5023,7 @@ num_entries(int infotype, char *bufstart, char *end_of_buf, char **lastentry, len = le32_to_cpu(dir_info->FileNameLength); if (len < 0 || - entryptr + len < entryptr || + add_would_overflow(entryptr, len) || entryptr + len > end_of_buf || entryptr + len + size > end_of_buf) { cifs_dbg(VFS, "directory entry name would overflow frame end of buf %p\n",