KMSAN reports an uninitialized value issue in dma_map_phys()[1]. This is a false positive caused by the way the virtual address is handled in kmsan_handle_dma(). Fix it by translating the physical address to a virtual address using phys_to_virt(). [1] BUG: KMSAN: uninit-value in dma_map_phys+0xdc5/0x1060 dma_map_phys+0xdc5/0x1060 dma_map_page_attrs+0xcf/0x130 e1000_xmit_frame+0x3c51/0x78f0 dev_hard_start_xmit+0x22f/0xa30 sch_direct_xmit+0x3b2/0xcf0 __dev_queue_xmit+0x3588/0x5e60 neigh_resolve_output+0x9c5/0xaf0 ip6_finish_output2+0x24e0/0x2d30 ip6_finish_output+0x903/0x10d0 ip6_output+0x331/0x600 mld_sendpack+0xb4a/0x1770 mld_ifc_work+0x1328/0x19b0 process_scheduled_works+0xb91/0x1d80 worker_thread+0xedf/0x1590 kthread+0xd5c/0xf00 ret_from_fork+0x1f5/0x4c0 ret_from_fork_asm+0x1a/0x30 Uninit was created at: __kmalloc_cache_noprof+0x8f5/0x16b0 syslog_print+0x9a/0xef0 do_syslog+0x849/0xfe0 __x64_sys_syslog+0x97/0x100 x64_sys_call+0x3cf8/0x3e30 do_syscall_64+0xd9/0xfa0 entry_SYSCALL_64_after_hwframe+0x77/0x7f Bytes 0-89 of 90 are uninitialized Memory access of size 90 starts at ffff8880367ed000 CPU: 1 UID: 0 PID: 1552 Comm: kworker/1:2 Not tainted 6.17.0-next-20250929 #26 PREEMPT(none) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-5.fc42 04/01/2014 Workqueue: mld mld_ifc_work Fixes: 6eb1e769b2c1 ("kmsan: convert kmsan_handle_dma to use physical addresses") Signed-off-by: Shigeru Yoshida --- The hash in the "Fixes" tag comes from the linux-next tree (next-20250929), as it has not yet been included in the mainline tree. --- mm/kmsan/hooks.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/mm/kmsan/hooks.c b/mm/kmsan/hooks.c index 90bee565b9bc..2cee59d89c80 100644 --- a/mm/kmsan/hooks.c +++ b/mm/kmsan/hooks.c @@ -339,13 +339,12 @@ static void kmsan_handle_dma_page(const void *addr, size_t size, void kmsan_handle_dma(phys_addr_t phys, size_t size, enum dma_data_direction dir) { - struct page *page = phys_to_page(phys); u64 page_offset, to_go; void *addr; if (PhysHighMem(phys)) return; - addr = page_to_virt(page); + addr = phys_to_virt(phys); /* * The kernel may occasionally give us adjacent DMA pages not belonging * to the same allocation. Process them separately to avoid triggering -- 2.51.0