<feed xmlns='http://www.w3.org/2005/Atom'>
<title>kernel/linux.git/include, branch v6.1.85</title>
<subtitle>Linux kernel stable tree (mirror)</subtitle>
<id>https://git.radix-linux.su/kernel/linux.git/atom?h=v6.1.85</id>
<link rel='self' href='https://git.radix-linux.su/kernel/linux.git/atom?h=v6.1.85'/>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/'/>
<updated>2024-04-10T14:28:34+00:00</updated>
<entry>
<title>mm/secretmem: fix GUP-fast succeeding on secretmem folios</title>
<updated>2024-04-10T14:28:34+00:00</updated>
<author>
<name>David Hildenbrand</name>
<email>david@redhat.com</email>
</author>
<published>2024-03-26T14:32:08+00:00</published>
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<id>urn:sha1:9c2b4b657739ecda38e3b383354a29566955ac48</id>
<content type='text'>
commit 65291dcfcf8936e1b23cfd7718fdfde7cfaf7706 upstream.

folio_is_secretmem() currently relies on secretmem folios being LRU
folios, to save some cycles.

However, folios might reside in a folio batch without the LRU flag set, or
temporarily have their LRU flag cleared.  Consequently, the LRU flag is
unreliable for this purpose.

In particular, this is the case when secretmem_fault() allocates a fresh
page and calls filemap_add_folio()-&gt;folio_add_lru().  The folio might be
added to the per-cpu folio batch and won't get the LRU flag set until the
batch was drained using e.g., lru_add_drain().

Consequently, folio_is_secretmem() might not detect secretmem folios and
GUP-fast can succeed in grabbing a secretmem folio, crashing the kernel
when we would later try reading/writing to the folio, because the folio
has been unmapped from the directmap.

Fix it by removing that unreliable check.

Link: https://lkml.kernel.org/r/20240326143210.291116-2-david@redhat.com
Fixes: 1507f51255c9 ("mm: introduce memfd_secret system call to create "secret" memory areas")
Signed-off-by: David Hildenbrand &lt;david@redhat.com&gt;
Reported-by: xingwei lee &lt;xrivendell7@gmail.com&gt;
Reported-by: yue sun &lt;samsun1006219@gmail.com&gt;
Closes: https://lore.kernel.org/lkml/CABOYnLyevJeravW=QrH0JUPYEcDN160aZFb7kwndm-J2rmz0HQ@mail.gmail.com/
Debugged-by: Miklos Szeredi &lt;miklos@szeredi.hu&gt;
Tested-by: Miklos Szeredi &lt;mszeredi@redhat.com&gt;
Reviewed-by: Mike Rapoport (IBM) &lt;rppt@kernel.org&gt;
Cc: Lorenzo Stoakes &lt;lstoakes@gmail.com&gt;
Cc: &lt;stable@vger.kernel.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: David Hildenbrand &lt;david@redhat.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>driver core: Introduce device_link_wait_removal()</title>
<updated>2024-04-10T14:28:32+00:00</updated>
<author>
<name>Herve Codina</name>
<email>herve.codina@bootlin.com</email>
</author>
<published>2024-03-25T15:21:25+00:00</published>
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<id>urn:sha1:9406d598a13ad4e0f13b63d3a2bdbaf30d73af44</id>
<content type='text'>
commit 0462c56c290a99a7f03e817ae5b843116dfb575c upstream.

The commit 80dd33cf72d1 ("drivers: base: Fix device link removal")
introduces a workqueue to release the consumer and supplier devices used
in the devlink.
In the job queued, devices are release and in turn, when all the
references to these devices are dropped, the release function of the
device itself is called.

Nothing is present to provide some synchronisation with this workqueue
in order to ensure that all ongoing releasing operations are done and
so, some other operations can be started safely.

For instance, in the following sequence:
  1) of_platform_depopulate()
  2) of_overlay_remove()

During the step 1, devices are released and related devlinks are removed
(jobs pushed in the workqueue).
During the step 2, OF nodes are destroyed but, without any
synchronisation with devlink removal jobs, of_overlay_remove() can raise
warnings related to missing of_node_put():
  ERROR: memory leak, expected refcount 1 instead of 2

Indeed, the missing of_node_put() call is going to be done, too late,
from the workqueue job execution.

Introduce device_link_wait_removal() to offer a way to synchronize
operations waiting for the end of devlink removals (i.e. end of
workqueue jobs).
Also, as a flushing operation is done on the workqueue, the workqueue
used is moved from a system-wide workqueue to a local one.

Cc: stable@vger.kernel.org
Signed-off-by: Herve Codina &lt;herve.codina@bootlin.com&gt;
Tested-by: Luca Ceresoli &lt;luca.ceresoli@bootlin.com&gt;
Reviewed-by: Nuno Sa &lt;nuno.sa@analog.com&gt;
Reviewed-by: Saravana Kannan &lt;saravanak@google.com&gt;
Acked-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
Link: https://lore.kernel.org/r/20240325152140.198219-2-herve.codina@bootlin.com
Signed-off-by: Rob Herring &lt;robh@kernel.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>udp: do not accept non-tunnel GSO skbs landing in a tunnel</title>
<updated>2024-04-10T14:28:27+00:00</updated>
<author>
<name>Antoine Tenart</name>
<email>atenart@kernel.org</email>
</author>
<published>2024-03-26T11:33:58+00:00</published>
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<id>urn:sha1:d12245080cb259d82b34699f6cd4ec11bdb688bd</id>
<content type='text'>
commit 3d010c8031e39f5fa1e8b13ada77e0321091011f upstream.

When rx-udp-gro-forwarding is enabled UDP packets might be GROed when
being forwarded. If such packets might land in a tunnel this can cause
various issues and udp_gro_receive makes sure this isn't the case by
looking for a matching socket. This is performed in
udp4/6_gro_lookup_skb but only in the current netns. This is an issue
with tunneled packets when the endpoint is in another netns. In such
cases the packets will be GROed at the UDP level, which leads to various
issues later on. The same thing can happen with rx-gro-list.

We saw this with geneve packets being GROed at the UDP level. In such
case gso_size is set; later the packet goes through the geneve rx path,
the geneve header is pulled, the offset are adjusted and frag_list skbs
are not adjusted with regard to geneve. When those skbs hit
skb_fragment, it will misbehave. Different outcomes are possible
depending on what the GROed skbs look like; from corrupted packets to
kernel crashes.

One example is a BUG_ON[1] triggered in skb_segment while processing the
frag_list. Because gso_size is wrong (geneve header was pulled)
skb_segment thinks there is "geneve header size" of data in frag_list,
although it's in fact the next packet. The BUG_ON itself has nothing to
do with the issue. This is only one of the potential issues.

Looking up for a matching socket in udp_gro_receive is fragile: the
lookup could be extended to all netns (not speaking about performances)
but nothing prevents those packets from being modified in between and we
could still not find a matching socket. It's OK to keep the current
logic there as it should cover most cases but we also need to make sure
we handle tunnel packets being GROed too early.

This is done by extending the checks in udp_unexpected_gso: GSO packets
lacking the SKB_GSO_UDP_TUNNEL/_CSUM bits and landing in a tunnel must
be segmented.

[1] kernel BUG at net/core/skbuff.c:4408!
    RIP: 0010:skb_segment+0xd2a/0xf70
    __udp_gso_segment+0xaa/0x560

Fixes: 9fd1ff5d2ac7 ("udp: Support UDP fraglist GRO/GSO.")
Fixes: 36707061d6ba ("udp: allow forwarding of plain (non-fraglisted) UDP GRO packets")
Signed-off-by: Antoine Tenart &lt;atenart@kernel.org&gt;
Reviewed-by: Willem de Bruijn &lt;willemb@google.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>Bluetooth: add quirk for broken address properties</title>
<updated>2024-04-10T14:28:24+00:00</updated>
<author>
<name>Johan Hovold</name>
<email>johan+linaro@kernel.org</email>
</author>
<published>2024-03-20T07:55:53+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=3e773d04aef9c9e0cdf97cfd23bc82c52305e0a7'/>
<id>urn:sha1:3e773d04aef9c9e0cdf97cfd23bc82c52305e0a7</id>
<content type='text'>
commit 39646f29b100566451d37abc4cc8cdd583756dfe upstream.

Some Bluetooth controllers lack persistent storage for the device
address and instead one can be provided by the boot firmware using the
'local-bd-address' devicetree property.

The Bluetooth devicetree bindings clearly states that the address should
be specified in little-endian order, but due to a long-standing bug in
the Qualcomm driver which reversed the address some boot firmware has
been providing the address in big-endian order instead.

Add a new quirk that can be set on platforms with broken firmware and
use it to reverse the address when parsing the property so that the
underlying driver bug can be fixed.

Fixes: 5c0a1001c8be ("Bluetooth: hci_qca: Add helper to set device address")
Cc: stable@vger.kernel.org      # 5.1
Reviewed-by: Douglas Anderson &lt;dianders@chromium.org&gt;
Signed-off-by: Johan Hovold &lt;johan+linaro@kernel.org&gt;
Signed-off-by: Luiz Augusto von Dentz &lt;luiz.von.dentz@intel.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>KVM: arm64: Fix host-programmed guest events in nVHE</title>
<updated>2024-04-10T14:28:23+00:00</updated>
<author>
<name>Oliver Upton</name>
<email>oliver.upton@linux.dev</email>
</author>
<published>2024-03-05T18:48:39+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=923579201dece7cb9fc30662b4f6e7d7801042a8'/>
<id>urn:sha1:923579201dece7cb9fc30662b4f6e7d7801042a8</id>
<content type='text'>
commit e89c928bedd77d181edc2df01cb6672184775140 upstream.

Programming PMU events in the host that count during guest execution is
a feature supported by perf, e.g.

  perf stat -e cpu_cycles:G ./lkvm run

While this works for VHE, the guest/host event bitmaps are not carried
through to the hypervisor in the nVHE configuration. Make
kvm_pmu_update_vcpu_events() conditional on whether or not _hardware_
supports PMUv3 rather than if the vCPU as vPMU enabled.

Cc: stable@vger.kernel.org
Fixes: 84d751a019a9 ("KVM: arm64: Pass pmu events to hyp via vcpu")
Reviewed-by: Marc Zyngier &lt;maz@kernel.org&gt;
Link: https://lore.kernel.org/r/20240305184840.636212-3-oliver.upton@linux.dev
Signed-off-by: Oliver Upton &lt;oliver.upton@linux.dev&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>inet: inet_defrag: prevent sk release while still in use</title>
<updated>2024-04-10T14:28:23+00:00</updated>
<author>
<name>Florian Westphal</name>
<email>fw@strlen.de</email>
</author>
<published>2024-03-26T10:18:41+00:00</published>
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<id>urn:sha1:7d0567842b78390dd9b60f00f1d8f838d540e325</id>
<content type='text'>
[ Upstream commit 18685451fc4e546fc0e718580d32df3c0e5c8272 ]

ip_local_out() and other functions can pass skb-&gt;sk as function argument.

If the skb is a fragment and reassembly happens before such function call
returns, the sk must not be released.

This affects skb fragments reassembled via netfilter or similar
modules, e.g. openvswitch or ct_act.c, when run as part of tx pipeline.

Eric Dumazet made an initial analysis of this bug.  Quoting Eric:
  Calling ip_defrag() in output path is also implying skb_orphan(),
  which is buggy because output path relies on sk not disappearing.

  A relevant old patch about the issue was :
  8282f27449bf ("inet: frag: Always orphan skbs inside ip_defrag()")

  [..]

  net/ipv4/ip_output.c depends on skb-&gt;sk being set, and probably to an
  inet socket, not an arbitrary one.

  If we orphan the packet in ipvlan, then downstream things like FQ
  packet scheduler will not work properly.

  We need to change ip_defrag() to only use skb_orphan() when really
  needed, ie whenever frag_list is going to be used.

Eric suggested to stash sk in fragment queue and made an initial patch.
However there is a problem with this:

If skb is refragmented again right after, ip_do_fragment() will copy
head-&gt;sk to the new fragments, and sets up destructor to sock_wfree.
IOW, we have no choice but to fix up sk_wmem accouting to reflect the
fully reassembled skb, else wmem will underflow.

This change moves the orphan down into the core, to last possible moment.
As ip_defrag_offset is aliased with sk_buff-&gt;sk member, we must move the
offset into the FRAG_CB, else skb-&gt;sk gets clobbered.

This allows to delay the orphaning long enough to learn if the skb has
to be queued or if the skb is completing the reasm queue.

In the former case, things work as before, skb is orphaned.  This is
safe because skb gets queued/stolen and won't continue past reasm engine.

In the latter case, we will steal the skb-&gt;sk reference, reattach it to
the head skb, and fix up wmem accouting when inet_frag inflates truesize.

Fixes: 7026b1ddb6b8 ("netfilter: Pass socket pointer down through okfn().")
Diagnosed-by: Eric Dumazet &lt;edumazet@google.com&gt;
Reported-by: xingwei lee &lt;xrivendell7@gmail.com&gt;
Reported-by: yue sun &lt;samsun1006219@gmail.com&gt;
Reported-by: syzbot+e5167d7144a62715044c@syzkaller.appspotmail.com
Signed-off-by: Florian Westphal &lt;fw@strlen.de&gt;
Reviewed-by: Eric Dumazet &lt;edumazet@google.com&gt;
Link: https://lore.kernel.org/r/20240326101845.30836-1-fw@strlen.de
Signed-off-by: Paolo Abeni &lt;pabeni@redhat.com&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
</entry>
<entry>
<title>tcp: properly terminate timers for kernel sockets</title>
<updated>2024-04-10T14:28:21+00:00</updated>
<author>
<name>Eric Dumazet</name>
<email>edumazet@google.com</email>
</author>
<published>2024-03-22T13:57:32+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=91b243de910a9ac8476d40238ab3dbfeedd5b7de'/>
<id>urn:sha1:91b243de910a9ac8476d40238ab3dbfeedd5b7de</id>
<content type='text'>
[ Upstream commit 151c9c724d05d5b0dd8acd3e11cb69ef1f2dbada ]

We had various syzbot reports about tcp timers firing after
the corresponding netns has been dismantled.

Fortunately Josef Bacik could trigger the issue more often,
and could test a patch I wrote two years ago.

When TCP sockets are closed, we call inet_csk_clear_xmit_timers()
to 'stop' the timers.

inet_csk_clear_xmit_timers() can be called from any context,
including when socket lock is held.
This is the reason it uses sk_stop_timer(), aka del_timer().
This means that ongoing timers might finish much later.

For user sockets, this is fine because each running timer
holds a reference on the socket, and the user socket holds
a reference on the netns.

For kernel sockets, we risk that the netns is freed before
timer can complete, because kernel sockets do not hold
reference on the netns.

This patch adds inet_csk_clear_xmit_timers_sync() function
that using sk_stop_timer_sync() to make sure all timers
are terminated before the kernel socket is released.
Modules using kernel sockets close them in their netns exit()
handler.

Also add sock_not_owned_by_me() helper to get LOCKDEP
support : inet_csk_clear_xmit_timers_sync() must not be called
while socket lock is held.

It is very possible we can revert in the future commit
3a58f13a881e ("net: rds: acquire refcount on TCP sockets")
which attempted to solve the issue in rds only.
(net/smc/af_smc.c and net/mptcp/subflow.c have similar code)

We probably can remove the check_net() tests from
tcp_out_of_resources() and __tcp_close() in the future.

Reported-by: Josef Bacik &lt;josef@toxicpanda.com&gt;
Closes: https://lore.kernel.org/netdev/20240314210740.GA2823176@perftesting/
Fixes: 26abe14379f8 ("net: Modify sk_alloc to not reference count the netns of kernel sockets.")
Fixes: 8a68173691f0 ("net: sk_clone_lock() should only do get_net() if the parent is not a kernel socket")
Link: https://lore.kernel.org/bpf/CANn89i+484ffqb93aQm1N-tjxxvb3WDKX0EbD7318RwRgsatjw@mail.gmail.com/
Signed-off-by: Eric Dumazet &lt;edumazet@google.com&gt;
Tested-by: Josef Bacik &lt;josef@toxicpanda.com&gt;
Cc: Tetsuo Handa &lt;penguin-kernel@I-love.SAKURA.ne.jp&gt;
Link: https://lore.kernel.org/r/20240322135732.1535772-1-edumazet@google.com
Signed-off-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
</entry>
<entry>
<title>scsi: sd: Fix TCG OPAL unlock on system resume</title>
<updated>2024-04-03T13:19:51+00:00</updated>
<author>
<name>Damien Le Moal</name>
<email>dlemoal@kernel.org</email>
</author>
<published>2024-03-19T07:12:09+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=3e284e15b7f05ed1e74ebcdc5d9db6b6e78fcb17'/>
<id>urn:sha1:3e284e15b7f05ed1e74ebcdc5d9db6b6e78fcb17</id>
<content type='text'>
commit 0c76106cb97548810214def8ee22700bbbb90543 upstream.

Commit 3cc2ffe5c16d ("scsi: sd: Differentiate system and runtime start/stop
management") introduced the manage_system_start_stop scsi_device flag to
allow libata to indicate to the SCSI disk driver that nothing should be
done when resuming a disk on system resume. This change turned the
execution of sd_resume() into a no-op for ATA devices on system
resume. While this solved deadlock issues during device resume, this change
also wrongly removed the execution of opal_unlock_from_suspend().  As a
result, devices with TCG OPAL locking enabled remain locked and
inaccessible after a system resume from sleep.

To fix this issue, introduce the SCSI driver resume method and implement it
with the sd_resume() function calling opal_unlock_from_suspend(). The
former sd_resume() function is renamed to sd_resume_common() and modified
to call the new sd_resume() function. For non-ATA devices, this result in
no functional changes.

In order for libata to explicitly execute sd_resume() when a device is
resumed during system restart, the function scsi_resume_device() is
introduced. libata calls this function from the revalidation work executed
on devie resume, a state that is indicated with the new device flag
ATA_DFLAG_RESUMING. Doing so, locked TCG OPAL enabled devices are unlocked
on resume, allowing normal operation.

Fixes: 3cc2ffe5c16d ("scsi: sd: Differentiate system and runtime start/stop management")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=218538
Cc: stable@vger.kernel.org
Signed-off-by: Damien Le Moal &lt;dlemoal@kernel.org&gt;
Link: https://lore.kernel.org/r/20240319071209.1179257-1-dlemoal@kernel.org
Signed-off-by: Martin K. Petersen &lt;martin.petersen@oracle.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>vfio: Introduce interface to flush virqfd inject workqueue</title>
<updated>2024-04-03T13:19:46+00:00</updated>
<author>
<name>Alex Williamson</name>
<email>alex.williamson@redhat.com</email>
</author>
<published>2024-03-29T21:38:51+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=33dc33f560017ffdf7a3db03b963f407082aab16'/>
<id>urn:sha1:33dc33f560017ffdf7a3db03b963f407082aab16</id>
<content type='text'>
[ Upstream commit b620ecbd17a03cacd06f014a5d3f3a11285ce053 ]

In order to synchronize changes that can affect the thread callback,
introduce an interface to force a flush of the inject workqueue.  The
irqfd pointer is only valid under spinlock, but the workqueue cannot
be flushed under spinlock.  Therefore the flush work for the irqfd is
queued under spinlock.  The vfio_irqfd_cleanup_wq workqueue is re-used
for queuing this work such that flushing the workqueue is also ordered
relative to shutdown.

Reviewed-by: Kevin Tian &lt;kevin.tian@intel.com&gt;
Reviewed-by: Reinette Chatre &lt;reinette.chatre@intel.com&gt;
Reviewed-by: Eric Auger &lt;eric.auger@redhat.com&gt;
Link: https://lore.kernel.org/r/20240308230557.805580-4-alex.williamson@redhat.com
Signed-off-by: Alex Williamson &lt;alex.williamson@redhat.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
</entry>
<entry>
<title>minmax: add umin(a, b) and umax(a, b)</title>
<updated>2024-04-03T13:19:44+00:00</updated>
<author>
<name>David Laight</name>
<email>David.Laight@ACULAB.COM</email>
</author>
<published>2023-09-18T08:16:30+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/kernel/linux.git/commit/?id=8d8be62a7d5386fe224c5455361da980ce64a96f'/>
<id>urn:sha1:8d8be62a7d5386fe224c5455361da980ce64a96f</id>
<content type='text'>
[ Upstream commit 80fcac55385ccb710d33a20dc1caaef29bd5a921 ]

Patch series "minmax: Relax type checks in min() and max()", v4.

The min() (etc) functions in minmax.h require that the arguments have
exactly the same types.

However when the type check fails, rather than look at the types and fix
the type of a variable/constant, everyone seems to jump on min_t().  In
reality min_t() ought to be rare - when something unusual is being done,
not normality.

The orginal min() (added in 2.4.9) replaced several inline functions and
included the type - so matched the implicit casting of the function call.
This was renamed min_t() in 2.4.10 and the current min() added.  There is
no actual indication that the conversion of negatve values to large
unsigned values has ever been an actual problem.

A quick grep shows 5734 min() and 4597 min_t().  Having the casts on
almost half of the calls shows that something is clearly wrong.

If the wrong type is picked (and it is far too easy to pick the type of
the result instead of the larger input) then significant bits can get
discarded.

Pretty much the worst example is in the derived clamp_val(), consider:
        unsigned char x = 200u;
        y = clamp_val(x, 10u, 300u);

I also suspect that many of the min_t(u16, ...) are actually wrong.  For
example copy_data() in printk_ringbuffer.c contains:

        data_size = min_t(u16, buf_size, len);

Here buf_size is 'unsigned int' and len 'u16', pass a 64k buffer (can you
prove that doesn't happen?) and no data is returned.  Apparantly it did -
and has since been fixed.

The only reason that most of the min_t() are 'fine' is that pretty much
all the values in the kernel are between 0 and INT_MAX.

Patch 1 adds umin(), this uses integer promotions to convert both
arguments to 'unsigned long long'.  It can be used to compare a signed
type that is known to contain a non-negative value with an unsigned type.
The compiler typically optimises it all away.  Added first so that it can
be referred to in patch 2.

Patch 2 replaces the 'same type' check with a 'same signedness' one.  This
makes min(unsigned_int_var, sizeof()) be ok.  The error message is also
improved and will contain the expanded form of both arguments (useful for
seeing how constants are defined).

Patch 3 just fixes some whitespace.

Patch 4 allows comparisons of 'unsigned char' and 'unsigned short' to
signed types.  The integer promotion rules convert them both to 'signed
int' prior to the comparison so they can never cause a negative value be
converted to a large positive one.

Patch 5 (rewritted for v4) allows comparisons of unsigned values against
non-negative constant integer expressions.  This makes
min(unsigned_int_var, 4) be ok.

The only common case that is still errored is the comparison of signed
values against unsigned constant integer expressions below __INT_MAX__.
Typcally min(int_val, sizeof (foo)), the real fix for this is casting the
constant: min(int_var, (int)sizeof (foo)).

With all the patches applied pretty much all the min_t() could be replaced
by min(), and most of the rest by umin().  However they all need careful
inspection due to code like:

        sz = min_t(unsigned char, sz - 1, LIM - 1) + 1;

which converts 0 to LIM.

This patch (of 6):

umin() and umax() can be used when min()/max() errors a signed v unsigned
compare when the signed value is known to be non-negative.

Unlike min_t(some_unsigned_type, a, b) umin() will never mask off high
bits if an inappropriate type is selected.

The '+ 0u + 0ul + 0ull' may look strange.
The '+ 0u' is needed for 'signed int' on 64bit systems.
The '+ 0ul' is needed for 'signed long' on 32bit systems.
The '+ 0ull' is needed for 'signed long long'.

Link: https://lkml.kernel.org/r/b97faef60ad24922b530241c5d7c933c@AcuMS.aculab.com
Link: https://lkml.kernel.org/r/41d93ca827a248698ec64bf57e0c05a5@AcuMS.aculab.com
Signed-off-by: David Laight &lt;david.laight@aculab.com&gt;
Cc: Andy Shevchenko &lt;andriy.shevchenko@linux.intel.com&gt;
Cc: Christoph Hellwig &lt;hch@infradead.org&gt;
Cc: Jason A. Donenfeld &lt;Jason@zx2c4.com&gt;
Cc: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Cc: Matthew Wilcox (Oracle) &lt;willy@infradead.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Stable-dep-of: 51b30ecb73b4 ("swiotlb: Fix alignment checks when both allocation and DMA masks are present")
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
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