[PATCH 00/44] Change a lot of min_t() that might mask high bits

[PATCH 00/44] Change a lot of min_t() that might mask high bits

[david.laight.linux]

From: David Laight <david.laight.linux@gmail.com>

It in not uncommon for code to use min_t(uint, a, b) when one of a or b
is 64bit and can have a value that is larger than 2^32;
This is particularly prevelant with:
	uint_var = min_t(uint, uint_var, uint64_expression);

Casts to u8 and u16 are very likely to discard significant bits.

These can be detected at compile time by changing min_t(), for example:
#define CHECK_SIZE(fn, type, val) \
	BUILD_BUG_ON_MSG(sizeof (val) > sizeof (type) && \
		!statically_true(((val) >> 8 * (sizeof (type) - 1)) < 256), \
		fn "() significant bits of '" #val "' may be discarded")

#define min_t(type, x, y) ({ \
	CHECK_SIZE("min_t", type, x); \
	CHECK_SIZE("min_t", type, y); \
	__cmp_once(min, type, x, y); })

(and similar changes to max_t() and clamp_t().)

This shows up some real bugs, some unlikely bugs and some false positives.
In most cases both arguments are unsigned type (just different ones)
and min_t() can just be replaced by min().

The patches are all independant and are most of the ones needed to
get the x86-64 kernel I build to compile.
I've not tried building an allyesconfig or allmodconfig kernel.
I've also not included the patch to minmax.h itself.

I've tried to put the patches that actually fix things first.
The last one is 0009.

I gave up on fixing sched/fair.c - it is too broken for a single patch!
The patch for net/ipv4/tcp.c is also absent because do_tcp_getsockopt()
needs multiple/larger changes to make it 'sane'.

I've had to trim the 124 maintainers/lists that get_maintainer.pl finds
from 124 to under 100 to be able to send the cover letter.
The individual patches only go to the addresses found for the associated files.
That reduces the number of emails to a less unsane number.

David Laight (44):
  x86/asm/bitops: Change the return type of variable__ffs() to unsigned
    int
  ext4: Fix saturation of 64bit inode times for old filesystems
  perf: Fix branch stack callchain limit
  io_uring/net: Change some dubious min_t()
  ipc/msg: Fix saturation of percpu counts in msgctl_info()
  bpf: Verifier, remove some unusual uses of min_t() and max_t()
  net/core/flow_dissector: Fix cap of __skb_flow_dissect() return value.
  net: ethtool: Use min3() instead of nested min_t(u16,...)
  ipv6: __ip6_append_data() don't abuse max_t() casts
  x86/crypto: ctr_crypt() use min() instead of min_t()
  arch/x96/kvm: use min() instead of min_t()
  block: use min() instead of min_t()
  drivers/acpi: use min() instead of min_t()
  drivers/char/hw_random: use min3() instead of nested min_t()
  drivers/char/tpm: use min() instead of min_t()
  drivers/crypto/ccp: use min() instead of min_t()
  drivers/cxl: use min() instead of min_t()
  drivers/gpio: use min() instead of min_t()
  drivers/gpu/drm/amd: use min() instead of min_t()
  drivers/i2c/busses: use min() instead of min_t()
  drivers/net/ethernet/realtek: use min() instead of min_t()
  drivers/nvme: use min() instead of min_t()
  arch/x86/mm: use min() instead of min_t()
  drivers/nvmem: use min() instead of min_t()
  drivers/pci: use min() instead of min_t()
  drivers/scsi: use min() instead of min_t()
  drivers/tty/vt: use umin() instead of min_t(u16, ...) for row/col
    limits
  drivers/usb/storage: use min() instead of min_t()
  drivers/xen: use min() instead of min_t()
  fs: use min() or umin() instead of min_t()
  block: bvec.h: use min() instead of min_t()
  nodemask: use min() instead of min_t()
  ipc: use min() instead of min_t()
  bpf: use min() instead of min_t()
  bpf_trace: use min() instead of min_t()
  lib/bucket_locks: use min() instead of min_t()
  lib/crypto/mpi: use min() instead of min_t()
  lib/dynamic_queue_limits: use max() instead of max_t()
  mm: use min() instead of min_t()
  net: Don't pass bitfields to max_t()
  net/core: Change loop conditions so min() can be used
  net: use min() instead of min_t()
  net/netlink: Use umin() to avoid min_t(int, ...) discarding high bits
  net/mptcp: Change some dubious min_t(int, ...) to min()

 arch/x86/crypto/aesni-intel_glue.c            |  3 +-
 arch/x86/include/asm/bitops.h                 | 18 +++++-------
 arch/x86/kvm/emulate.c                        |  3 +-
 arch/x86/kvm/lapic.c                          |  2 +-
 arch/x86/kvm/mmu/mmu.c                        |  2 +-
 arch/x86/mm/pat/set_memory.c                  | 12 ++++----
 block/blk-iocost.c                            |  6 ++--
 block/blk-settings.c                          |  2 +-
 block/partitions/efi.c                        |  3 +-
 drivers/acpi/property.c                       |  2 +-
 drivers/char/hw_random/core.c                 |  2 +-
 drivers/char/tpm/tpm1-cmd.c                   |  2 +-
 drivers/char/tpm/tpm_tis_core.c               |  4 +--
 drivers/crypto/ccp/ccp-dev.c                  |  2 +-
 drivers/cxl/core/mbox.c                       |  2 +-
 drivers/gpio/gpiolib-acpi-core.c              |  2 +-
 .../gpu/drm/amd/amdgpu/amdgpu_doorbell_mgr.c  |  4 +--
 drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c        |  2 +-
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |  2 +-
 drivers/i2c/busses/i2c-designware-master.c    |  2 +-
 drivers/net/ethernet/realtek/r8169_main.c     |  3 +-
 drivers/nvme/host/pci.c                       |  3 +-
 drivers/nvme/host/zns.c                       |  3 +-
 drivers/nvmem/core.c                          |  2 +-
 drivers/pci/probe.c                           |  3 +-
 drivers/scsi/hosts.c                          |  2 +-
 drivers/tty/vt/selection.c                    |  9 +++---
 drivers/usb/storage/protocol.c                |  3 +-
 drivers/xen/grant-table.c                     |  2 +-
 fs/buffer.c                                   |  2 +-
 fs/exec.c                                     |  2 +-
 fs/ext4/ext4.h                                |  2 +-
 fs/ext4/mballoc.c                             |  3 +-
 fs/ext4/resize.c                              |  2 +-
 fs/ext4/super.c                               |  2 +-
 fs/fat/dir.c                                  |  4 +--
 fs/fat/file.c                                 |  3 +-
 fs/fuse/dev.c                                 |  2 +-
 fs/fuse/file.c                                |  8 ++---
 fs/splice.c                                   |  2 +-
 include/linux/bvec.h                          |  3 +-
 include/linux/nodemask.h                      |  9 +++---
 include/linux/perf_event.h                    |  2 +-
 include/net/tcp_ecn.h                         |  5 ++--
 io_uring/net.c                                |  6 ++--
 ipc/mqueue.c                                  |  4 +--
 ipc/msg.c                                     |  6 ++--
 kernel/bpf/core.c                             |  4 +--
 kernel/bpf/log.c                              |  2 +-
 kernel/bpf/verifier.c                         | 29 +++++++------------
 kernel/trace/bpf_trace.c                      |  2 +-
 lib/bucket_locks.c                            |  2 +-
 lib/crypto/mpi/mpicoder.c                     |  2 +-
 lib/dynamic_queue_limits.c                    |  2 +-
 mm/gup.c                                      |  4 +--
 mm/memblock.c                                 |  2 +-
 mm/memory.c                                   |  2 +-
 mm/percpu.c                                   |  2 +-
 mm/truncate.c                                 |  3 +-
 mm/vmscan.c                                   |  2 +-
 net/core/datagram.c                           |  6 ++--
 net/core/flow_dissector.c                     |  7 ++---
 net/core/net-sysfs.c                          |  3 +-
 net/core/skmsg.c                              |  4 +--
 net/ethtool/cmis_cdb.c                        |  7 ++---
 net/ipv4/fib_trie.c                           |  2 +-
 net/ipv4/tcp_input.c                          |  4 +--
 net/ipv4/tcp_output.c                         |  5 ++--
 net/ipv4/tcp_timer.c                          |  4 +--
 net/ipv6/addrconf.c                           |  8 ++---
 net/ipv6/ip6_output.c                         |  7 +++--
 net/ipv6/ndisc.c                              |  5 ++--
 net/mptcp/protocol.c                          |  8 ++---
 net/netlink/genetlink.c                       |  9 +++---
 net/packet/af_packet.c                        |  2 +-
 net/unix/af_unix.c                            |  4 +--
 76 files changed, 141 insertions(+), 176 deletions(-)

-- 
2.39.5

[PATCH 44/44] net/mptcp: Change some dubious min_t(int, ...) to min()

[david.laight.linux]

From: David Laight <david.laight.linux@gmail.com>

There are two:
	min_t(int, xxx, mptcp_wnd_end(msk) - msk->snd_nxt);
Both mptcp_wnd_end(msk) and msk->snd_nxt are u64, their difference
(aka the window size) might be limited to 32 bits - but that isn't
knowable from this code.
So checks being added to min_t() detect the potential discard of
significant bits.

Provided the 'avail_size' and return of mptcp_check_allowed_size()
are changed to an unsigned type (size_t matches the type the caller
uses) both min_t() can be changed to min().

Signed-off-by: David Laight <david.laight.linux@gmail.com>
---
 net/mptcp/protocol.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 2d6b8de35c44..d57c3659462f 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1123,8 +1123,8 @@ struct mptcp_sendmsg_info {
 	bool data_lock_held;
 };
 
-static int mptcp_check_allowed_size(const struct mptcp_sock *msk, struct sock *ssk,
-				    u64 data_seq, int avail_size)
+static size_t mptcp_check_allowed_size(const struct mptcp_sock *msk, struct sock *ssk,
+				       u64 data_seq, size_t avail_size)
 {
 	u64 window_end = mptcp_wnd_end(msk);
 	u64 mptcp_snd_wnd;
@@ -1133,7 +1133,7 @@ static int mptcp_check_allowed_size(const struct mptcp_sock *msk, struct sock *s
 		return avail_size;
 
 	mptcp_snd_wnd = window_end - data_seq;
-	avail_size = min_t(unsigned int, mptcp_snd_wnd, avail_size);
+	avail_size = min(mptcp_snd_wnd, avail_size);
 
 	if (unlikely(tcp_sk(ssk)->snd_wnd < mptcp_snd_wnd)) {
 		tcp_sk(ssk)->snd_wnd = min_t(u64, U32_MAX, mptcp_snd_wnd);
@@ -1477,7 +1477,7 @@ struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
 	if (!ssk || !sk_stream_memory_free(ssk))
 		return NULL;
 
-	burst = min_t(int, MPTCP_SEND_BURST_SIZE, mptcp_wnd_end(msk) - msk->snd_nxt);
+	burst = min(MPTCP_SEND_BURST_SIZE, mptcp_wnd_end(msk) - msk->snd_nxt);
 	wmem = READ_ONCE(ssk->sk_wmem_queued);
 	if (!burst)
 		return ssk;
-- 
2.39.5

Re: [PATCH 00/44] Change a lot of min_t() that might mask high bits

[Jakub Kicinski]

On Wed, 19 Nov 2025 22:40:56 +0000 david.laight.linux@gmail.com wrote:
> I've had to trim the 124 maintainers/lists that get_maintainer.pl finds
> from 124 to under 100 to be able to send the cover letter.
> The individual patches only go to the addresses found for the associated files.
> That reduces the number of emails to a less unsane number.

Please split the networking (9?) patches out to a separate series.
It will help you with the CC list, and help us to get this applied..

Re: [PATCH 00/44] Change a lot of min_t() that might mask high bits

[Lorenzo Stoakes]

On Wed, Nov 19, 2025 at 10:40:56PM +0000, david.laight.linux@gmail.com wrote:
> From: David Laight <david.laight.linux@gmail.com>
>
> It in not uncommon for code to use min_t(uint, a, b) when one of a or b
> is 64bit and can have a value that is larger than 2^32;
> This is particularly prevelant with:
> 	uint_var = min_t(uint, uint_var, uint64_expression);
>
> Casts to u8 and u16 are very likely to discard significant bits.
>
> These can be detected at compile time by changing min_t(), for example:
> #define CHECK_SIZE(fn, type, val) \
> 	BUILD_BUG_ON_MSG(sizeof (val) > sizeof (type) && \
> 		!statically_true(((val) >> 8 * (sizeof (type) - 1)) < 256), \
> 		fn "() significant bits of '" #val "' may be discarded")
>
> #define min_t(type, x, y) ({ \
> 	CHECK_SIZE("min_t", type, x); \
> 	CHECK_SIZE("min_t", type, y); \
> 	__cmp_once(min, type, x, y); })
>
> (and similar changes to max_t() and clamp_t().)

Have we made sure that the introduction of these don't cause a combinatorial
explosion like previous min()/max() changes did?

>
> This shows up some real bugs, some unlikely bugs and some false positives.
> In most cases both arguments are unsigned type (just different ones)
> and min_t() can just be replaced by min().
>
> The patches are all independant and are most of the ones needed to
> get the x86-64 kernel I build to compile.
> I've not tried building an allyesconfig or allmodconfig kernel.

Well I have a beefy box at my disposal so tried thiese for you :)

Both allyesconfig & allmodconfig works fine for x86-64 (I tried both for good
measure)

> I've also not included the patch to minmax.h itself.
>
> I've tried to put the patches that actually fix things first.
> The last one is 0009.
>
> I gave up on fixing sched/fair.c - it is too broken for a single patch!
> The patch for net/ipv4/tcp.c is also absent because do_tcp_getsockopt()
> needs multiple/larger changes to make it 'sane'.

I guess this isn't broken per se there just retain min_t()/max_t() right?

>
> I've had to trim the 124 maintainers/lists that get_maintainer.pl finds
> from 124 to under 100 to be able to send the cover letter.
> The individual patches only go to the addresses found for the associated files.
> That reduces the number of emails to a less unsane number.
>
> David Laight (44):
>   x86/asm/bitops: Change the return type of variable__ffs() to unsigned
>     int
>   ext4: Fix saturation of 64bit inode times for old filesystems
>   perf: Fix branch stack callchain limit
>   io_uring/net: Change some dubious min_t()
>   ipc/msg: Fix saturation of percpu counts in msgctl_info()
>   bpf: Verifier, remove some unusual uses of min_t() and max_t()
>   net/core/flow_dissector: Fix cap of __skb_flow_dissect() return value.
>   net: ethtool: Use min3() instead of nested min_t(u16,...)
>   ipv6: __ip6_append_data() don't abuse max_t() casts
>   x86/crypto: ctr_crypt() use min() instead of min_t()
>   arch/x96/kvm: use min() instead of min_t()
>   block: use min() instead of min_t()
>   drivers/acpi: use min() instead of min_t()
>   drivers/char/hw_random: use min3() instead of nested min_t()
>   drivers/char/tpm: use min() instead of min_t()
>   drivers/crypto/ccp: use min() instead of min_t()
>   drivers/cxl: use min() instead of min_t()
>   drivers/gpio: use min() instead of min_t()
>   drivers/gpu/drm/amd: use min() instead of min_t()
>   drivers/i2c/busses: use min() instead of min_t()
>   drivers/net/ethernet/realtek: use min() instead of min_t()
>   drivers/nvme: use min() instead of min_t()
>   arch/x86/mm: use min() instead of min_t()
>   drivers/nvmem: use min() instead of min_t()
>   drivers/pci: use min() instead of min_t()
>   drivers/scsi: use min() instead of min_t()
>   drivers/tty/vt: use umin() instead of min_t(u16, ...) for row/col
>     limits
>   drivers/usb/storage: use min() instead of min_t()
>   drivers/xen: use min() instead of min_t()
>   fs: use min() or umin() instead of min_t()
>   block: bvec.h: use min() instead of min_t()
>   nodemask: use min() instead of min_t()
>   ipc: use min() instead of min_t()
>   bpf: use min() instead of min_t()
>   bpf_trace: use min() instead of min_t()
>   lib/bucket_locks: use min() instead of min_t()
>   lib/crypto/mpi: use min() instead of min_t()
>   lib/dynamic_queue_limits: use max() instead of max_t()
>   mm: use min() instead of min_t()
>   net: Don't pass bitfields to max_t()
>   net/core: Change loop conditions so min() can be used
>   net: use min() instead of min_t()
>   net/netlink: Use umin() to avoid min_t(int, ...) discarding high bits
>   net/mptcp: Change some dubious min_t(int, ...) to min()
>
>  arch/x86/crypto/aesni-intel_glue.c            |  3 +-
>  arch/x86/include/asm/bitops.h                 | 18 +++++-------
>  arch/x86/kvm/emulate.c                        |  3 +-
>  arch/x86/kvm/lapic.c                          |  2 +-
>  arch/x86/kvm/mmu/mmu.c                        |  2 +-
>  arch/x86/mm/pat/set_memory.c                  | 12 ++++----
>  block/blk-iocost.c                            |  6 ++--
>  block/blk-settings.c                          |  2 +-
>  block/partitions/efi.c                        |  3 +-
>  drivers/acpi/property.c                       |  2 +-
>  drivers/char/hw_random/core.c                 |  2 +-
>  drivers/char/tpm/tpm1-cmd.c                   |  2 +-
>  drivers/char/tpm/tpm_tis_core.c               |  4 +--
>  drivers/crypto/ccp/ccp-dev.c                  |  2 +-
>  drivers/cxl/core/mbox.c                       |  2 +-
>  drivers/gpio/gpiolib-acpi-core.c              |  2 +-
>  .../gpu/drm/amd/amdgpu/amdgpu_doorbell_mgr.c  |  4 +--
>  drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c        |  2 +-
>  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |  2 +-
>  drivers/i2c/busses/i2c-designware-master.c    |  2 +-
>  drivers/net/ethernet/realtek/r8169_main.c     |  3 +-
>  drivers/nvme/host/pci.c                       |  3 +-
>  drivers/nvme/host/zns.c                       |  3 +-
>  drivers/nvmem/core.c                          |  2 +-
>  drivers/pci/probe.c                           |  3 +-
>  drivers/scsi/hosts.c                          |  2 +-
>  drivers/tty/vt/selection.c                    |  9 +++---
>  drivers/usb/storage/protocol.c                |  3 +-
>  drivers/xen/grant-table.c                     |  2 +-
>  fs/buffer.c                                   |  2 +-
>  fs/exec.c                                     |  2 +-
>  fs/ext4/ext4.h                                |  2 +-
>  fs/ext4/mballoc.c                             |  3 +-
>  fs/ext4/resize.c                              |  2 +-
>  fs/ext4/super.c                               |  2 +-
>  fs/fat/dir.c                                  |  4 +--
>  fs/fat/file.c                                 |  3 +-
>  fs/fuse/dev.c                                 |  2 +-
>  fs/fuse/file.c                                |  8 ++---
>  fs/splice.c                                   |  2 +-
>  include/linux/bvec.h                          |  3 +-
>  include/linux/nodemask.h                      |  9 +++---
>  include/linux/perf_event.h                    |  2 +-
>  include/net/tcp_ecn.h                         |  5 ++--
>  io_uring/net.c                                |  6 ++--
>  ipc/mqueue.c                                  |  4 +--
>  ipc/msg.c                                     |  6 ++--
>  kernel/bpf/core.c                             |  4 +--
>  kernel/bpf/log.c                              |  2 +-
>  kernel/bpf/verifier.c                         | 29 +++++++------------
>  kernel/trace/bpf_trace.c                      |  2 +-
>  lib/bucket_locks.c                            |  2 +-
>  lib/crypto/mpi/mpicoder.c                     |  2 +-
>  lib/dynamic_queue_limits.c                    |  2 +-
>  mm/gup.c                                      |  4 +--
>  mm/memblock.c                                 |  2 +-
>  mm/memory.c                                   |  2 +-
>  mm/percpu.c                                   |  2 +-
>  mm/truncate.c                                 |  3 +-
>  mm/vmscan.c                                   |  2 +-
>  net/core/datagram.c                           |  6 ++--
>  net/core/flow_dissector.c                     |  7 ++---
>  net/core/net-sysfs.c                          |  3 +-
>  net/core/skmsg.c                              |  4 +--
>  net/ethtool/cmis_cdb.c                        |  7 ++---
>  net/ipv4/fib_trie.c                           |  2 +-
>  net/ipv4/tcp_input.c                          |  4 +--
>  net/ipv4/tcp_output.c                         |  5 ++--
>  net/ipv4/tcp_timer.c                          |  4 +--
>  net/ipv6/addrconf.c                           |  8 ++---
>  net/ipv6/ip6_output.c                         |  7 +++--
>  net/ipv6/ndisc.c                              |  5 ++--
>  net/mptcp/protocol.c                          |  8 ++---
>  net/netlink/genetlink.c                       |  9 +++---
>  net/packet/af_packet.c                        |  2 +-
>  net/unix/af_unix.c                            |  4 +--
>  76 files changed, 141 insertions(+), 176 deletions(-)
>
> --
> 2.39.5
>

Re: (subset) [PATCH 00/44] Change a lot of min_t() that might mask high bits

[Jens Axboe]

On Wed, 19 Nov 2025 22:40:56 +0000, david.laight.linux@gmail.com wrote:
> It in not uncommon for code to use min_t(uint, a, b) when one of a or b
> is 64bit and can have a value that is larger than 2^32;
> This is particularly prevelant with:
> 	uint_var = min_t(uint, uint_var, uint64_expression);
> 
> Casts to u8 and u16 are very likely to discard significant bits.
> 
> [...]

Applied, thanks!

[12/44] block: use min() instead of min_t()
        commit: 9420e720ad192c53c8d2803c5a2313b2d586adbd

Best regards,
-- 
Jens Axboe

Re: [PATCH 00/44] Change a lot of min_t() that might mask high bits

[Herbert Xu]

On Wed, Nov 19, 2025 at 10:40:56PM +0000, david.laight.linux@gmail.com wrote:
> From: David Laight <david.laight.linux@gmail.com>
> 
> It in not uncommon for code to use min_t(uint, a, b) when one of a or b
> is 64bit and can have a value that is larger than 2^32;
> This is particularly prevelant with:
> 	uint_var = min_t(uint, uint_var, uint64_expression);
> 
> Casts to u8 and u16 are very likely to discard significant bits.
> 
> These can be detected at compile time by changing min_t(), for example:
> #define CHECK_SIZE(fn, type, val) \
> 	BUILD_BUG_ON_MSG(sizeof (val) > sizeof (type) && \
> 		!statically_true(((val) >> 8 * (sizeof (type) - 1)) < 256), \
> 		fn "() significant bits of '" #val "' may be discarded")
> 
> #define min_t(type, x, y) ({ \
> 	CHECK_SIZE("min_t", type, x); \
> 	CHECK_SIZE("min_t", type, y); \
> 	__cmp_once(min, type, x, y); })
> 
> (and similar changes to max_t() and clamp_t().)
> 
> This shows up some real bugs, some unlikely bugs and some false positives.
> In most cases both arguments are unsigned type (just different ones)
> and min_t() can just be replaced by min().
> 
> The patches are all independant and are most of the ones needed to
> get the x86-64 kernel I build to compile.
> I've not tried building an allyesconfig or allmodconfig kernel.
> I've also not included the patch to minmax.h itself.
> 
> I've tried to put the patches that actually fix things first.
> The last one is 0009.
> 
> I gave up on fixing sched/fair.c - it is too broken for a single patch!
> The patch for net/ipv4/tcp.c is also absent because do_tcp_getsockopt()
> needs multiple/larger changes to make it 'sane'.
> 
> I've had to trim the 124 maintainers/lists that get_maintainer.pl finds
> from 124 to under 100 to be able to send the cover letter.
> The individual patches only go to the addresses found for the associated files.
> That reduces the number of emails to a less unsane number.
> 
> David Laight (44):
>   x86/asm/bitops: Change the return type of variable__ffs() to unsigned
>     int
>   ext4: Fix saturation of 64bit inode times for old filesystems
>   perf: Fix branch stack callchain limit
>   io_uring/net: Change some dubious min_t()
>   ipc/msg: Fix saturation of percpu counts in msgctl_info()
>   bpf: Verifier, remove some unusual uses of min_t() and max_t()
>   net/core/flow_dissector: Fix cap of __skb_flow_dissect() return value.
>   net: ethtool: Use min3() instead of nested min_t(u16,...)
>   ipv6: __ip6_append_data() don't abuse max_t() casts
>   x86/crypto: ctr_crypt() use min() instead of min_t()
>   arch/x96/kvm: use min() instead of min_t()
>   block: use min() instead of min_t()
>   drivers/acpi: use min() instead of min_t()
>   drivers/char/hw_random: use min3() instead of nested min_t()
>   drivers/char/tpm: use min() instead of min_t()
>   drivers/crypto/ccp: use min() instead of min_t()
>   drivers/cxl: use min() instead of min_t()
>   drivers/gpio: use min() instead of min_t()
>   drivers/gpu/drm/amd: use min() instead of min_t()
>   drivers/i2c/busses: use min() instead of min_t()
>   drivers/net/ethernet/realtek: use min() instead of min_t()
>   drivers/nvme: use min() instead of min_t()
>   arch/x86/mm: use min() instead of min_t()
>   drivers/nvmem: use min() instead of min_t()
>   drivers/pci: use min() instead of min_t()
>   drivers/scsi: use min() instead of min_t()
>   drivers/tty/vt: use umin() instead of min_t(u16, ...) for row/col
>     limits
>   drivers/usb/storage: use min() instead of min_t()
>   drivers/xen: use min() instead of min_t()
>   fs: use min() or umin() instead of min_t()
>   block: bvec.h: use min() instead of min_t()
>   nodemask: use min() instead of min_t()
>   ipc: use min() instead of min_t()
>   bpf: use min() instead of min_t()
>   bpf_trace: use min() instead of min_t()
>   lib/bucket_locks: use min() instead of min_t()
>   lib/crypto/mpi: use min() instead of min_t()
>   lib/dynamic_queue_limits: use max() instead of max_t()
>   mm: use min() instead of min_t()
>   net: Don't pass bitfields to max_t()
>   net/core: Change loop conditions so min() can be used
>   net: use min() instead of min_t()
>   net/netlink: Use umin() to avoid min_t(int, ...) discarding high bits
>   net/mptcp: Change some dubious min_t(int, ...) to min()
> 
>  arch/x86/crypto/aesni-intel_glue.c            |  3 +-
>  arch/x86/include/asm/bitops.h                 | 18 +++++-------
>  arch/x86/kvm/emulate.c                        |  3 +-
>  arch/x86/kvm/lapic.c                          |  2 +-
>  arch/x86/kvm/mmu/mmu.c                        |  2 +-
>  arch/x86/mm/pat/set_memory.c                  | 12 ++++----
>  block/blk-iocost.c                            |  6 ++--
>  block/blk-settings.c                          |  2 +-
>  block/partitions/efi.c                        |  3 +-
>  drivers/acpi/property.c                       |  2 +-
>  drivers/char/hw_random/core.c                 |  2 +-
>  drivers/char/tpm/tpm1-cmd.c                   |  2 +-
>  drivers/char/tpm/tpm_tis_core.c               |  4 +--
>  drivers/crypto/ccp/ccp-dev.c                  |  2 +-
>  drivers/cxl/core/mbox.c                       |  2 +-
>  drivers/gpio/gpiolib-acpi-core.c              |  2 +-
>  .../gpu/drm/amd/amdgpu/amdgpu_doorbell_mgr.c  |  4 +--
>  drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c        |  2 +-
>  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |  2 +-
>  drivers/i2c/busses/i2c-designware-master.c    |  2 +-
>  drivers/net/ethernet/realtek/r8169_main.c     |  3 +-
>  drivers/nvme/host/pci.c                       |  3 +-
>  drivers/nvme/host/zns.c                       |  3 +-
>  drivers/nvmem/core.c                          |  2 +-
>  drivers/pci/probe.c                           |  3 +-
>  drivers/scsi/hosts.c                          |  2 +-
>  drivers/tty/vt/selection.c                    |  9 +++---
>  drivers/usb/storage/protocol.c                |  3 +-
>  drivers/xen/grant-table.c                     |  2 +-
>  fs/buffer.c                                   |  2 +-
>  fs/exec.c                                     |  2 +-
>  fs/ext4/ext4.h                                |  2 +-
>  fs/ext4/mballoc.c                             |  3 +-
>  fs/ext4/resize.c                              |  2 +-
>  fs/ext4/super.c                               |  2 +-
>  fs/fat/dir.c                                  |  4 +--
>  fs/fat/file.c                                 |  3 +-
>  fs/fuse/dev.c                                 |  2 +-
>  fs/fuse/file.c                                |  8 ++---
>  fs/splice.c                                   |  2 +-
>  include/linux/bvec.h                          |  3 +-
>  include/linux/nodemask.h                      |  9 +++---
>  include/linux/perf_event.h                    |  2 +-
>  include/net/tcp_ecn.h                         |  5 ++--
>  io_uring/net.c                                |  6 ++--
>  ipc/mqueue.c                                  |  4 +--
>  ipc/msg.c                                     |  6 ++--
>  kernel/bpf/core.c                             |  4 +--
>  kernel/bpf/log.c                              |  2 +-
>  kernel/bpf/verifier.c                         | 29 +++++++------------
>  kernel/trace/bpf_trace.c                      |  2 +-
>  lib/bucket_locks.c                            |  2 +-
>  lib/crypto/mpi/mpicoder.c                     |  2 +-
>  lib/dynamic_queue_limits.c                    |  2 +-
>  mm/gup.c                                      |  4 +--
>  mm/memblock.c                                 |  2 +-
>  mm/memory.c                                   |  2 +-
>  mm/percpu.c                                   |  2 +-
>  mm/truncate.c                                 |  3 +-
>  mm/vmscan.c                                   |  2 +-
>  net/core/datagram.c                           |  6 ++--
>  net/core/flow_dissector.c                     |  7 ++---
>  net/core/net-sysfs.c                          |  3 +-
>  net/core/skmsg.c                              |  4 +--
>  net/ethtool/cmis_cdb.c                        |  7 ++---
>  net/ipv4/fib_trie.c                           |  2 +-
>  net/ipv4/tcp_input.c                          |  4 +--
>  net/ipv4/tcp_output.c                         |  5 ++--
>  net/ipv4/tcp_timer.c                          |  4 +--
>  net/ipv6/addrconf.c                           |  8 ++---
>  net/ipv6/ip6_output.c                         |  7 +++--
>  net/ipv6/ndisc.c                              |  5 ++--
>  net/mptcp/protocol.c                          |  8 ++---
>  net/netlink/genetlink.c                       |  9 +++---
>  net/packet/af_packet.c                        |  2 +-
>  net/unix/af_unix.c                            |  4 +--
>  76 files changed, 141 insertions(+), 176 deletions(-)

Patches 10,14,16,37 applied.  Thanks.
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [PATCH 44/44] net/mptcp: Change some dubious min_t(int, ...) to min()

[Matthieu Baerts]

Hi David,

On 19/11/2025 23:41, david.laight.linux@gmail.com wrote:
> From: David Laight <david.laight.linux@gmail.com>
> 
> There are two:
> 	min_t(int, xxx, mptcp_wnd_end(msk) - msk->snd_nxt);
> Both mptcp_wnd_end(msk) and msk->snd_nxt are u64, their difference
> (aka the window size) might be limited to 32 bits - but that isn't
> knowable from this code.
> So checks being added to min_t() detect the potential discard of
> significant bits.
> 
> Provided the 'avail_size' and return of mptcp_check_allowed_size()
> are changed to an unsigned type (size_t matches the type the caller
> uses) both min_t() can be changed to min().

Thank you for the patch!

Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>

I'm not sure what the status on your side: I don't know if you still
plan to send a specific series for all the modifications in the net, but
just in case, I just applied your patch in the MPTCP tree. I removed the
"net/" prefix from the subject. I will send this patch with others for
including in the net-next tree later on if you didn't do that in between.

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.

Re: [PATCH 44/44] net/mptcp: Change some dubious min_t(int, ...) to min()

[David Laight]

On Thu, 18 Dec 2025 18:33:26 +0100
Matthieu Baerts <matttbe@kernel.org> wrote:

> Hi David,
> 
> On 19/11/2025 23:41, david.laight.linux@gmail.com wrote:
> > From: David Laight <david.laight.linux@gmail.com>
> > 
> > There are two:
> > 	min_t(int, xxx, mptcp_wnd_end(msk) - msk->snd_nxt);
> > Both mptcp_wnd_end(msk) and msk->snd_nxt are u64, their difference
> > (aka the window size) might be limited to 32 bits - but that isn't
> > knowable from this code.
> > So checks being added to min_t() detect the potential discard of
> > significant bits.
> > 
> > Provided the 'avail_size' and return of mptcp_check_allowed_size()
> > are changed to an unsigned type (size_t matches the type the caller
> > uses) both min_t() can be changed to min().  
> 
> Thank you for the patch!
> 
> Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
> 
> I'm not sure what the status on your side: I don't know if you still
> plan to send a specific series for all the modifications in the net, but
> just in case, I just applied your patch in the MPTCP tree. I removed the
> "net/" prefix from the subject. I will send this patch with others for
> including in the net-next tree later on if you didn't do that in between.

I'll go through them again at some point.
I'll check against 'next' (but probably not net-next).
I actually need to look at the ones that seemed like real bugs when I
did an allmodconfig build - that got to over 200 patches to get 'clean'.

It would be nice to get rid of a lot of the min_t(), but I might try
to attack the dubious ones rather than the ones that appear to make
no difference.

I might propose some extra checks in minmax.h that would break W=1 builds.
Detecting things like min_t(u8, u32_value, 0xff) where the cast makes the
comparison always succeed.
In reality any calls with casts to u8 and u16 are 'dubious'.

That and changing checkpatch.pl to not suggest min_t() at all, and
to reject the more dubious uses.
After all with:
	min(x, (int)y)
it is clear to the reader that 'y' is being possibly truncated and converted
to a signed value, but with:
	min_t(int, x, y)
you don't know which value needed the cast (and the line isn't even shorter).
But what I've found all to often is actually:
	a = min_t(typeof(a), x, y);
and the similar:
	x = min_t(typeof(x), x, y);
where the type of the result is used and high bits get discarded.

I've just been trying to build with #define clamp_val clamp.
That requires a few minor changes and I'm pretty sure shows up
a real bug.

	David

> 
> Cheers,
> Matt

Re: [PATCH 44/44] net/mptcp: Change some dubious min_t(int, ...) to min()

[Matthieu Baerts]

Hi David,

Thank you for your reply!

On 18/12/2025 21:15, David Laight wrote:
> On Thu, 18 Dec 2025 18:33:26 +0100
> Matthieu Baerts <matttbe@kernel.org> wrote:
> 
>> Hi David,
>>
>> On 19/11/2025 23:41, david.laight.linux@gmail.com wrote:
>>> From: David Laight <david.laight.linux@gmail.com>
>>>
>>> There are two:
>>> 	min_t(int, xxx, mptcp_wnd_end(msk) - msk->snd_nxt);
>>> Both mptcp_wnd_end(msk) and msk->snd_nxt are u64, their difference
>>> (aka the window size) might be limited to 32 bits - but that isn't
>>> knowable from this code.
>>> So checks being added to min_t() detect the potential discard of
>>> significant bits.
>>>
>>> Provided the 'avail_size' and return of mptcp_check_allowed_size()
>>> are changed to an unsigned type (size_t matches the type the caller
>>> uses) both min_t() can be changed to min().  
>>
>> Thank you for the patch!
>>
>> Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
>>
>> I'm not sure what the status on your side: I don't know if you still
>> plan to send a specific series for all the modifications in the net, but
>> just in case, I just applied your patch in the MPTCP tree. I removed the
>> "net/" prefix from the subject. I will send this patch with others for
>> including in the net-next tree later on if you didn't do that in between.
> 
> I'll go through them again at some point.

Great, thank you!

> I'll check against 'next' (but probably not net-next).

net-next is in linux-next, so that should be fine.

> I actually need to look at the ones that seemed like real bugs when I
> did an allmodconfig build - that got to over 200 patches to get 'clean'.
> 
> It would be nice to get rid of a lot of the min_t(), but I might try
> to attack the dubious ones rather than the ones that appear to make
> no difference.
> 
> I might propose some extra checks in minmax.h that would break W=1 builds.
> Detecting things like min_t(u8, u32_value, 0xff) where the cast makes the
> comparison always succeed.
> In reality any calls with casts to u8 and u16 are 'dubious'.
> 
> That and changing checkpatch.pl to not suggest min_t() at all, and
> to reject the more dubious uses.
> After all with:
> 	min(x, (int)y)
> it is clear to the reader that 'y' is being possibly truncated and converted
> to a signed value, but with:
> 	min_t(int, x, y)
> you don't know which value needed the cast (and the line isn't even shorter).
> But what I've found all to often is actually:
> 	a = min_t(typeof(a), x, y);
> and the similar:
> 	x = min_t(typeof(x), x, y);
> where the type of the result is used and high bits get discarded.

Good idea to add extra checks and prevent future issues!
> I've just been trying to build with #define clamp_val clamp.
> That requires a few minor changes and I'm pretty sure shows up
> a real bug.

Thank you for looking at that!

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.