[xen stable-4.18] x86/ioapic: Fix signed shifts in io_apic.c

[patchbot@xxxxxxx]

commit 0dc5fbee17cd2bcb1aa6a1cf420dd80381587de8
Author:     Matthew Barnes <matthew.barnes@xxxxxxxxx>
AuthorDate: Thu Jul 4 14:11:03 2024 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Jul 4 14:11:03 2024 +0200

    x86/ioapic: Fix signed shifts in io_apic.c
    
    There exists bitshifts in the IOAPIC code where signed integers are
    shifted to the left by up to 31 bits, which is undefined behaviour.
    
    This patch fixes this by changing the integers from signed to unsigned.
    
    Signed-off-by: Matthew Barnes <matthew.barnes@xxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: c5746b021e573184fb92b601a0e93a295485054e
    master date: 2024-06-21 15:09:26 +0100
---
 xen/arch/x86/io_apic.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/io_apic.c b/xen/arch/x86/io_apic.c
index 0ef61fb2f1..c5342789e8 100644
--- a/xen/arch/x86/io_apic.c
+++ b/xen/arch/x86/io_apic.c
@@ -1692,7 +1692,8 @@ static void cf_check mask_and_ack_level_ioapic_irq(struct 
irq_desc *desc)
        !io_apic_level_ack_pending(desc->irq))
         move_masked_irq(desc);
 
-    if ( !(v & (1 << (i & 0x1f))) ) {
+    if ( !(v & (1U << (i & 0x1f))) )
+    {
         spin_lock(&ioapic_lock);
         __edge_IO_APIC_irq(desc->irq);
         __level_IO_APIC_irq(desc->irq);
@@ -1756,7 +1757,8 @@ static void cf_check end_level_ioapic_irq_new(struct 
irq_desc *desc, u8 vector)
          !io_apic_level_ack_pending(desc->irq) )
         move_native_irq(desc);
 
-    if (!(v & (1 << (i & 0x1f)))) {
+    if ( !(v & (1U << (i & 0x1f))) )
+    {
         spin_lock(&ioapic_lock);
         __mask_IO_APIC_irq(desc->irq);
         __edge_IO_APIC_irq(desc->irq);
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.18