CVE-2026-63794

*** Pendiente de traducción *** In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> KVM: SVM: Fix page overflow in sev_dbg_crypt() for ENCRYPT path<br /> <br /> In sev_dbg_crypt(), the per-iteration transfer length is bounded by<br /> the source page offset (PAGE_SIZE - s_off) but not by the destination<br /> page offset (PAGE_SIZE - d_off). When d_off &gt; s_off, the encrypt<br /> path (__sev_dbg_encrypt_user) performs a read-modify-write using a<br /> single-page intermediate buffer (dst_tpage):<br /> <br /> 1. __sev_dbg_decrypt() expands the size to round_up(len + (d_off &amp; 15), 16)<br /> before issuing the PSP command. If len + (d_off &amp; 15) &gt; PAGE_SIZE,<br /> the PSP writes beyond the end of the 4096-byte dst_tpage allocation.<br /> <br /> 2. The subsequent memcpy()/copy_from_user() into<br /> page_address(dst_tpage) + (d_off &amp; 15) of &amp;#39;len&amp;#39; bytes overflows<br /> by up to 15 bytes under the same condition.<br /> <br /> Trigger example: s_off = 0, d_off = 1, debug.len = PAGE_SIZE -<br /> the PSP is instructed to write round_up(4097, 16) = 4112 bytes to<br /> a 4096-byte buffer.<br /> <br /> Fix by also bounding len by (PAGE_SIZE - d_off), the same check that<br /> sev_send_update_data() already performs for its single-page guest<br /> region.<br /> <br /> ==================================================================<br /> BUG: KASAN: slab-use-after-free in sev_dbg_crypt+0x993/0xd10 [kvm_amd]<br /> Write of size 4095 at addr ff110062293bb009 by task sev_dbg_test/228214<br /> <br /> CPU: 96 UID: 0 PID: 228214 Comm: sev_dbg_test Tainted: G U W 7.0.0-smp--5ce9b0c48211-dbg #156 PREEMPTLAZY<br /> Tainted: [U]=USER, [W]=WARN<br /> Hardware name: Google Astoria/astoria, BIOS 0.20250817.1-0 08/25/2025<br /> Call Trace:<br /> <br /> dump_stack_lvl+0x54/0x70<br /> print_report+0xbc/0x260<br /> kasan_report+0xa2/0xd0<br /> kasan_check_range+0x25f/0x2c0<br /> __asan_memcpy+0x40/0x70<br /> sev_dbg_crypt+0x993/0xd10 [kvm_amd]<br /> sev_mem_enc_ioctl+0x33c/0x450 [kvm_amd]<br /> kvm_vm_ioctl+0x65d/0x6d0 [kvm]<br /> __se_sys_ioctl+0xb2/0x100<br /> do_syscall_64+0xe8/0x870<br /> entry_SYSCALL_64_after_hwframe+0x4b/0x53<br /> <br /> <br /> The buggy address belongs to the physical page:<br /> page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x7fe72b6a0 pfn:0x62293bb<br /> memcg:ff11000112827d82<br /> flags: 0x1400000000000000(node=1|zone=1)<br /> raw: 1400000000000000 0000000000000000 dead000000000122 0000000000000000<br /> raw: 00000007fe72b6a0 0000000000000000 00000001ffffffff ff11000112827d82<br /> page dumped because: kasan: bad access detected<br /> <br /> Memory state around the buggy address:<br /> ff110062293bbf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00<br /> ff110062293bbf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00<br /> &gt;ff110062293bc000: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc<br /> ^<br /> ff110062293bc080: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc<br /> ff110062293bc100: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc<br /> ==================================================================<br /> Disabling lock debugging due to kernel taint<br /> <br /> [sean: add sample KASAN splat, Fixes, and stable@]