[xen staging] xsm/flask: Fix undefined behaviour in avc_dump_av()

[patchbot@xxxxxxx]

commit 4f9457ece11a6231b7a17a11a873b8b4b9376fdc
Author:     Dmytro Prokopchuk <dmytro_prokopchuk1@xxxxxxxx>
AuthorDate: Wed May 6 14:00:58 2026 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed May 6 15:11:18 2026 +0200

    xsm/flask: Fix undefined behaviour in avc_dump_av()
    
    When booting Xen with CONFIG_USBAN=y and CONFIG_XSM_FLASK=y,
    UBSAN reports undefined behaviour in avc_dump_av() due to a left
    shift on a signed int:
    
    (XEN) [    1.104348] 
================================================================================
    (XEN) [    1.105096] UBSAN: Undefined behaviour in xsm/flask/avc.c:184:14
    (XEN) [    1.106052] left shift of 1073741824 by 1 places cannot be 
represented in type 'int'
    (XEN) [    1.107546] Xen WARN at common/ubsan/ubsan.c:176
    (XEN) [    1.108295] ----[ Xen-4.21.1  arm64  debug=y ubsan=y  Not tainted 
]----
    (XEN) [    1.108848] CPU:    0
    (XEN) [    1.109147] PC:     00000a00002f64fc 
ubsan.c#ubsan_epilogue+0x10/0xd4
    [...]
    (XEN) [    1.146320] Xen call trace:
    (XEN) [    1.146663]    [<00000a00002f64fc>] 
ubsan.c#ubsan_epilogue+0x10/0xd4 (PC)
    (XEN) [    1.147227]    [<00000a00002f7bc4>] 
__ubsan_handle_shift_out_of_bounds+0x1a0/0x290 (LR)
    (XEN) [    1.147868]
    (XEN) [    1.148177] 
================================================================================
    
    This can be solved by making 'perm' an unsigned 32-bit type (u32).
    
    Signed-off-by: Dmytro Prokopchuk <dmytro_prokopchuk1@xxxxxxxx>
    Acked-by: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>
---
 xen/xsm/flask/avc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/xen/xsm/flask/avc.c b/xen/xsm/flask/avc.c
index 3d39e55cae..6e1972d21b 100644
--- a/xen/xsm/flask/avc.c
+++ b/xen/xsm/flask/avc.c
@@ -152,7 +152,8 @@ static void __attribute__ ((format (printf, 2, 3)))
  */
 static void avc_dump_av(struct avc_dump_buf *buf, u16 tclass, u32 av)
 {
-    int i, i2, perm;
+    int i, i2;
+    uint32_t perm;
 
     if ( av == 0 )
     {
--
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