| Message ID | 20240123002814.1396804-60-keescook@chromium.org (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | overflow: Refactor open-coded arithmetic wrap-around | expand |
Kees Cook <keescook@chromium.org> writes: > 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: Michael Ellerman <mpe@ellerman.id.au> > Cc: Nicholas Piggin <npiggin@gmail.com> > Cc: Christophe Leroy <christophe.leroy@csgroup.eu> > Cc: "Aneesh Kumar K.V" <aneesh.kumar@kernel.org> > Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com> > Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com> > Cc: Vasant Hegde <hegdevasant@linux.vnet.ibm.com> > Cc: dingsenjie <dingsenjie@yulong.com> > Cc: linuxppc-dev@lists.ozlabs.org > Cc: Aneesh Kumar K.V <aneesh.kumar@kernel.org> > Cc: Naveen N. Rao <naveen.n.rao@linux.ibm.com> > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > arch/powerpc/platforms/powernv/opal-prd.c | 2 +- > arch/powerpc/xmon/xmon.c | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc) cheers
diff --git a/arch/powerpc/platforms/powernv/opal-prd.c b/arch/powerpc/platforms/powernv/opal-prd.c index b66b06efcef1..eaf95dc82925 100644 --- a/arch/powerpc/platforms/powernv/opal-prd.c +++ b/arch/powerpc/platforms/powernv/opal-prd.c @@ -51,7 +51,7 @@ static bool opal_prd_range_is_valid(uint64_t addr, uint64_t size) struct device_node *parent, *node; bool found; - if (addr + size < addr) + if (add_would_overflow(addr, size)) return false; parent = of_find_node_by_path("/reserved-memory"); diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c index b3b94cd37713..b91fdda49434 100644 --- a/arch/powerpc/xmon/xmon.c +++ b/arch/powerpc/xmon/xmon.c @@ -3252,7 +3252,7 @@ memzcan(void) } else if (!ok && ook) printf("%.8lx\n", a - mskip); ook = ok; - if (a + mskip < a) + if (add_would_overflow(a, mskip)) break; } if (ook)
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: Michael Ellerman <mpe@ellerman.id.au> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Christophe Leroy <christophe.leroy@csgroup.eu> Cc: "Aneesh Kumar K.V" <aneesh.kumar@kernel.org> Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com> Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com> Cc: Vasant Hegde <hegdevasant@linux.vnet.ibm.com> Cc: dingsenjie <dingsenjie@yulong.com> Cc: linuxppc-dev@lists.ozlabs.org Cc: Aneesh Kumar K.V <aneesh.kumar@kernel.org> Cc: Naveen N. Rao <naveen.n.rao@linux.ibm.com> Signed-off-by: Kees Cook <keescook@chromium.org> --- arch/powerpc/platforms/powernv/opal-prd.c | 2 +- arch/powerpc/xmon/xmon.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)