On 05/07/25 at 10:59pm, Andrew Morton wrote: > On Thu, 8 May 2025 12:25:15 +0800 Coiby Xu <c...@redhat.com> wrote: > > > > > > >Acked-by: Baoquan He <b...@redhat.com> > > > > Hi Andrew, > > > > It seems this patch was missed. > > January 2024. Yes, it's fair to assume that it was missed ;) > > > Will you pick it up? > > Sure. > > > Without this patch, > > kdump kernel will fail to be loaded by the kexec_file_load, > > > > [ 139.736948] UBSAN: array-index-out-of-bounds in > > arch/x86/kernel/crash.c:350:25 > > [ 139.742360] index 0 is out of range for type 'range [*]' > > [ 139.745695] CPU: 0 UID: 0 PID: 5778 Comm: kexec Not tainted > > 6.15.0-0.rc3.20250425git02ddfb981de8.32.fc43.x86_64 #1 PREEMPT(lazy) > > [ 139.745698] Hardware name: Amazon EC2 c5.large/, BIOS 1.0 10/16/2017 > > [ 139.745699] Call Trace: > > [ 139.745700] <TASK> > > [ 139.745701] dump_stack_lvl+0x5d/0x80 > > [ 139.745706] ubsan_epilogue+0x5/0x2b > > [ 139.745709] __ubsan_handle_out_of_bounds.cold+0x54/0x59 > > [ 139.745711] crash_setup_memmap_entries+0x2d9/0x330 > > [ 139.745716] setup_boot_parameters+0xf8/0x6a0 > > [ 139.745720] bzImage64_load+0x41b/0x4e0 > > [ 139.745722] ? find_next_iomem_res+0x109/0x140 > > [ 139.745727] ? locate_mem_hole_callback+0x109/0x170 > > [ 139.745737] kimage_file_alloc_init+0x1ef/0x3e0 > > [ 139.745740] __do_sys_kexec_file_load+0x180/0x2f0 > > [ 139.745742] do_syscall_64+0x7b/0x160 > > [ 139.745745] ? do_user_addr_fault+0x21a/0x690 > > [ 139.745747] ? exc_page_fault+0x7e/0x1a0 > > [ 139.745749] entry_SYSCALL_64_after_hwframe+0x76/0x7e > > [ 139.745751] RIP: 0033:0x7f7712c84e4d > > > > Do we know why this has appeared at such a late date? The reporter > must be doing something rare. > > Baoquan, please re-review this? > > A -stable backport is clearly required. A Fixes: would be nice, but I > assume this goes back a long time so it isn't worth spending a lot of > time working out when this was introduced.
No need for stable kernel. The UBSAN only warns a potential risk, it won't happen in reality. I am talking to Coiby, he got it wrong about the testing result. He saw the UBSAN warning when UBSAN is enabled, while vmcore is till saved successfully. > > The patch needed a bit of work to apply to current code. I did the > below. It compiles. > > --- > a/arch/x86/kernel/crash.c~x86-kexec-fix-potential-cmem-ranges-out-of-bounds > +++ a/arch/x86/kernel/crash.c > @@ -165,8 +165,18 @@ static struct crash_mem *fill_up_crash_e > /* > * Exclusion of crash region and/or crashk_low_res may cause > * another range split. So add extra two slots here. > + * > + * Exclusion of low 1M may not cause another range split, because the > + * range of exclude is [0, 1M] and the condition for splitting a new > + * region is that the start, end parameters are both in a certain > + * existing region in cmem and cannot be equal to existing region's > + * start or end. Obviously, the start of [0, 1M] cannot meet this > + * condition. > + * > + * But in order to lest the low 1M could be changed in the future, > + * (e.g. [stare, 1M]), add a extra slot. > */ > - nr_ranges += 2; > + nr_ranges += 3; > cmem = vzalloc(struct_size(cmem, ranges, nr_ranges)); > if (!cmem) > return NULL; > @@ -317,9 +327,16 @@ int crash_setup_memmap_entries(struct ki > * split. So use two slots here. > */ > nr_ranges = 2; > - cmem = vzalloc(struct_size(cmem, ranges, nr_ranges)); > + /* > + * In the current x86 architecture code, the elfheader is always > + * allocated at crashk_res.start. But it depends on the allocation > + * position of elfheader in crashk_res. To avoid potential out of > + * bounds in future, add a extra slot. > + */ > + cmem = vzalloc(struct_size(cmem, ranges, 2)); > if (!cmem) > return -ENOMEM; > + cmem->max_nr_ranges = 2; > > cmem->max_nr_ranges = nr_ranges; > cmem->nr_ranges = 0; > _ >
