When the check_[op]_overflow() helpers were introduced, all arguments
were required to be the same type to make the fallback macros simpler.
However, now that the fallback macros have been removed[1], it is fine
to allow mixed types, which makes using the helpers much more useful,
as they can be used to test for type-based overflows (e.g. adding two
large ints but storing into a u8), as would be handy in the drm core[2].
Remove the restriction, and add additional self-tests that exercise
some of the mixed-type overflow cases, and double-check for accidental
macro side-effects.
[1] https://git.kernel.org/linus/4eb6bd55cfb22ffc20652732340c4962f3ac9a91
[2] https://lore.kernel.org/lkml/20220824084514.2261614-2-gwan-gyeong.mun@intel.com
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: linux-hardening@vger.kernel.org
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Reviewed-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Tested-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
There are two definitions of the is_signed_type() macro: one in
<linux/overflow.h> and a second definition in <linux/trace_events.h>.
As suggested by Linus Torvalds, move the definition of the
is_signed_type() macro into the <linux/compiler.h> header file. Change
the definition of the is_signed_type() macro to make sure that it does
not trigger any sparse warnings with future versions of sparse for
bitwise types. See also:
https://lore.kernel.org/all/CAHk-=whjH6p+qzwUdx5SOVVHjS3WvzJQr6mDUwhEyTf6pJWzaQ@mail.gmail.com/https://lore.kernel.org/all/CAHk-=wjQGnVfb4jehFR0XyZikdQvCZouE96xR_nnf5kqaM5qqQ@mail.gmail.com/
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Isabella Basso <isabbasso@riseup.net>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Sander Vanheule <sander@svanheule.net>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220826162116.1050972-3-bvanassche@acm.org
There have been cases where struct_size() (or flex_array_size()) needs
to be calculated for an initializer, which requires it be a constant
expression. This is possible when the "count" argument is a constant
expression, so provide this ability for the helpers.
Cc: Gustavo A. R. Silva <gustavoars@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Tested-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/lkml/20220210010407.GA701603@embeddedor
In order to perform more open-coded replacements of common allocation
size arithmetic, the kernel needs saturating (SIZE_MAX) helpers for
multiplication, addition, and subtraction. For example, it is common in
allocators, especially on realloc, to add to an existing size:
p = krealloc(map->patch,
sizeof(struct reg_sequence) * (map->patch_regs + num_regs),
GFP_KERNEL);
There is no existing saturating replacement for this calculation, and
just leaving the addition open coded inside array_size() could
potentially overflow as well. For example, an overflow in an expression
for a size_t argument might wrap to zero:
array_size(anything, something_at_size_max + 1) == 0
Introduce size_mul(), size_add(), and size_sub() helpers that
implicitly promote arguments to size_t and saturated calculations for
use in allocations. With these helpers it is also possible to redefine
array_size(), array3_size(), flex_array_size(), and struct_size() in
terms of the new helpers.
As with the check_*_overflow() helpers, the new helpers use __must_check,
though what is really desired is a way to make sure that assignment is
only to a size_t lvalue. Without this, it's still possible to introduce
overflow/underflow via type conversion (i.e. from size_t to int).
Enforcing this will currently need to be left to static analysis or
future use of -Wconversion.
Additionally update the overflow unit tests to force runtime evaluation
for the pathological cases.
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Gustavo A. R. Silva <gustavoars@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Keith Busch <kbusch@kernel.org>
Cc: Len Baker <len.baker@gmx.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Once upgrading the minimum supported version of GCC to 5.1, we can drop
the fallback code for !COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW.
This is effectively a revert of commit f0907827a8 ("compiler.h: enable
builtin overflow checkers and add fallback code")
Link: https://github.com/ClangBuiltLinux/linux/issues/1438#issuecomment-916745801
Suggested-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
A 'false' return means the value was safely set, so the comment should
say 'true' for when it is not considered safe.
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Fixes: 0c66847793 ("overflow.h: Add arithmetic shift helper")
Link: https://lore.kernel.org/r/20210401160629.1941787-1-kbusch@kernel.org
The typical set of driver updates across the subsystem:
- Driver minor changes and bug fixes for mlx5, efa, rxe, vmw_pvrdma, hns,
usnic, qib, qedr, cxgb4, hns, bnxt_re
- Various rtrs fixes and updates
- Bug fix for mlx4 CM emulation for virtualization scenarios where MRA
wasn't working right
- Use tracepoints instead of pr_debug in the CM code
- Scrub the locking in ucma and cma to close more syzkaller bugs
- Use tasklet_setup in the subsystem
- Revert the idea that 'destroy' operations are not allowed to fail at
the driver level. This proved unworkable from a HW perspective.
- Revise how the umem API works so drivers make fewer mistakes using it
- XRC support for qedr
- Convert uverbs objects RWQ and MW to new the allocation scheme
- Large queue entry sizes for hns
- Use hmm_range_fault() for mlx5 On Demand Paging
- uverbs APIs to inspect the GID table instead of sysfs
- Move some of the RDMA code for building large page SGLs into
lib/scatterlist
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma
Pull rdma updates from Jason Gunthorpe:
"A usual cycle for RDMA with a typical mix of driver and core subsystem
updates:
- Driver minor changes and bug fixes for mlx5, efa, rxe, vmw_pvrdma,
hns, usnic, qib, qedr, cxgb4, hns, bnxt_re
- Various rtrs fixes and updates
- Bug fix for mlx4 CM emulation for virtualization scenarios where
MRA wasn't working right
- Use tracepoints instead of pr_debug in the CM code
- Scrub the locking in ucma and cma to close more syzkaller bugs
- Use tasklet_setup in the subsystem
- Revert the idea that 'destroy' operations are not allowed to fail
at the driver level. This proved unworkable from a HW perspective.
- Revise how the umem API works so drivers make fewer mistakes using
it
- XRC support for qedr
- Convert uverbs objects RWQ and MW to new the allocation scheme
- Large queue entry sizes for hns
- Use hmm_range_fault() for mlx5 On Demand Paging
- uverbs APIs to inspect the GID table instead of sysfs
- Move some of the RDMA code for building large page SGLs into
lib/scatterlist"
* tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma: (191 commits)
RDMA/ucma: Fix use after free in destroy id flow
RDMA/rxe: Handle skb_clone() failure in rxe_recv.c
RDMA/rxe: Move the definitions for rxe_av.network_type to uAPI
RDMA: Explicitly pass in the dma_device to ib_register_device
lib/scatterlist: Do not limit max_segment to PAGE_ALIGNED values
IB/mlx4: Convert rej_tmout radix-tree to XArray
RDMA/rxe: Fix bug rejecting all multicast packets
RDMA/rxe: Fix skb lifetime in rxe_rcv_mcast_pkt()
RDMA/rxe: Remove duplicate entries in struct rxe_mr
IB/hfi,rdmavt,qib,opa_vnic: Update MAINTAINERS
IB/rdmavt: Fix sizeof mismatch
MAINTAINERS: CISCO VIC LOW LATENCY NIC DRIVER
RDMA/bnxt_re: Fix sizeof mismatch for allocation of pbl_tbl.
RDMA/bnxt_re: Use rdma_umem_for_each_dma_block()
RDMA/umem: Move to allocate SG table from pages
lib/scatterlist: Add support in dynamic allocation of SG table from pages
tools/testing/scatterlist: Show errors in human readable form
tools/testing/scatterlist: Rejuvenate bit-rotten test
RDMA/ipoib: Set rtnl_link_ops for ipoib interfaces
RDMA/uverbs: Expose the new GID query API to user space
...
Since the destination variable of the check_*_overflow() helpers will
contain a wrapped value on failure, it would be best to make sure callers
really did check the return result of the helper. Adjust the macros to use
a bool-wrapping static inline that is marked with __must_check. This means
the macros can continue to have their type-agnostic behavior while gaining
the function attribute (that cannot be applied directly to macros).
Suggested-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Link: https://lore.kernel.org/lkml/202008151007.EF679DF@keescook/
Signed-off-by: Kees Cook <keescook@chromium.org>
The various array_size functions use SIZE_MAX define, but missed limits.h
causes to failure to compile code that needs overflow.h.
In file included from drivers/infiniband/core/uverbs_std_types_device.c:6:
./include/linux/overflow.h: In function 'array_size':
./include/linux/overflow.h:258:10: error: 'SIZE_MAX' undeclared (first use in this function)
258 | return SIZE_MAX;
| ^~~~~~~~
Fixes: 610b15c50e ("overflow.h: Add allocation size calculation helpers")
Link: https://lore.kernel.org/r/20200913102928.134985-1-leon@kernel.org
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Add flex_array_size() helper for the calculation of the size, in bytes,
of a flexible array member contained within an enclosing structure.
Example of usage:
struct something {
size_t count;
struct foo items[];
};
struct something *instance;
instance = kmalloc(struct_size(instance, items, count), GFP_KERNEL);
instance->count = count;
memcpy(instance->items, src, flex_array_size(instance, items, instance->count));
The helper returns SIZE_MAX on overflow instead of wrapping around.
Additionally replaces parameter "n" with "count" in struct_size() helper
for greater clarity and unification.
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20200609012233.GA3371@embeddedor
Signed-off-by: Kees Cook <keescook@chromium.org>
Pull core fixes from Ingo Molnar:
"A handful of objtool updates, plus a documentation addition for
__ab_c_size()"
* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
objtool: Fix whitelist documentation typo
objtool: Fix function fallthrough detection
objtool: Don't use ignore flag for fake jumps
overflow.h: Add comment documenting __ab_c_size()
__ab_c_size() is a somewhat opaque name. Document its purpose, and while
at it, rename the parameters to actually match the abc naming.
[ bp: glued a complete patch from chunks on LKML. ]
Reported-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Matthew Wilcox <willy@infradead.org>
Link: https://lkml.kernel.org/r/20190405045711.30339-1-bp@alien8.de
Add shift_overflow() helper to assist driver authors in ensuring that
shift operations don't cause overflows or other odd conditions.
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
[kees: tweaked comments and commit log, dropped unneeded assignment]
Signed-off-by: Kees Cook <keescook@chromium.org>
In preparation for replacing unchecked overflows for memory allocations,
this creates helpers for the 3 most common calculations:
array_size(a, b): 2-dimensional array
array3_size(a, b, c): 3-dimensional array
struct_size(ptr, member, n): struct followed by n-many trailing members
Each of these return SIZE_MAX on overflow instead of wrapping around.
(Additionally renames a variable named "array_size" to avoid future
collision.)
Co-developed-by: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
This adds wrappers for the __builtin overflow checkers present in gcc
5.1+ as well as fallback implementations for earlier compilers. It's not
that easy to implement the fully generic __builtin_X_overflow(T1 a, T2
b, T3 *d) in macros, so the fallback code assumes that T1, T2 and T3 are
the same. We obviously don't want the wrappers to have different
semantics depending on $GCC_VERSION, so we also insist on that even when
using the builtins.
There are a few problems with the 'a+b < a' idiom for checking for
overflow: For signed types, it relies on undefined behaviour and is
not actually complete (it doesn't check underflow;
e.g. INT_MIN+INT_MIN == 0 isn't caught). Due to type promotion it
is wrong for all types (signed and unsigned) narrower than
int. Similarly, when a and b does not have the same type, there are
subtle cases like
u32 a;
if (a + sizeof(foo) < a)
return -EOVERFLOW;
a += sizeof(foo);
where the test is always false on 64 bit platforms. Add to that that it
is not always possible to determine the types involved at a glance.
The new overflow.h is somewhat bulky, but that's mostly a result of
trying to be type-generic, complete (e.g. catching not only overflow
but also signed underflow) and not relying on undefined behaviour.
Linus is of course right [1] that for unsigned subtraction a-b, the
right way to check for overflow (underflow) is "b > a" and not
"__builtin_sub_overflow(a, b, &d)", but that's just one out of six cases
covered here, and included mostly for completeness.
So is it worth it? I think it is, if nothing else for the documentation
value of seeing
if (check_add_overflow(a, b, &d))
return -EGOAWAY;
do_stuff_with(d);
instead of the open-coded (and possibly wrong and/or incomplete and/or
UBsan-tickling)
if (a+b < a)
return -EGOAWAY;
do_stuff_with(a+b);
While gcc does recognize the 'a+b < a' idiom for testing unsigned add
overflow, it doesn't do nearly as good for unsigned multiplication
(there's also no single well-established idiom). So using
check_mul_overflow in kcalloc and friends may also make gcc generate
slightly better code.
[1] https://lkml.org/lkml/2015/11/2/658
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Kees Cook <keescook@chromium.org>
Kees Cook