[Crash-utility] Re: [PATCH] Fix "irq -a" exceeding the memory range issue

Hi Lianbo, On Wed, Jul 17, 2024 at 2:24 PM lijiang <lijiang(a)redhat.com&gt; wrote: > > On Wed, Jul 17, 2024 at 6:01 AM Tao Liu <ltao(a)redhat.com&gt; wrote: >> >> Hi Lianbo, >> >> On Tue, Jul 16, 2024 at 11:19 AM Tao Liu <ltao(a)redhat.com&gt; wrote: >> > >> > Hi Lianbo, >> > >> > On Fri, Jul 12, 2024 at 6:32 PM Lianbo Jiang <lijiang(a)redhat.com&gt; wrote: >> > > >> > > Hi, Tao >> > > >> > > On 7/5/24 9:26 AM, devel-request(a)lists.crash-utility.osci.io wrote: >> > > > Date: Thu, 4 Jul 2024 17:00:56 +1200 >> > > > From: Tao Liu&lt;ltao(a)redhat.com&gt; >> > > > Subject: [Crash-utility] [PATCH] Fix "irq -a" exceeding the memory >> > > > range issue >> > > > To:devel@lists.crash-utility.osci.io >> > > > Cc: Tao Liu&lt;ltao(a)redhat.com&gt; >> > > > Message-ID:<20240704050056.17375-1-ltao@redhat.com> >> > > > Content-Type: text/plain; charset="US-ASCII"; x-default=true >> > > > >> > > > Previously without the patch, there was an error observed as follows: >> > > > >> > > > crash> irq -a >> > > > IRQ NAME AFFINITY >> > > > 0 timer 0-191 >> > > > 4 ttyS0 0-23,96-119 >> > > > ... >> > > > 84 smartpqi 72-73,168 >> > > > irq: page excluded: kernel virtual address: ffff97d03ffff000 type: "irq_desc affinity" >> > > > >> > > > The reason is the reading of irq affinity exceeded the memory range, see >> > > > the following debug info: >> > > > >> > > > Thread 1 "crash" hit Breakpoint 1, generic_get_irq_affinity (irq=85) at kernel.c:7373 >> > > > 7375 irq_desc_addr = get_irq_desc_addr(irq); >> > > > (gdb) p/x irq_desc_addr >> > > > $1 = 0xffff97d03f21e800 >> > > > >> > > > crash> struct irq_desc 0xffff97d03f21e800 >> > > > struct irq_desc { >> > > > irq_common_data = { >> > > > state_use_accessors = 425755136, >> > > > node = 3, >> > > > handler_data = 0x0, >> > > > msi_desc = 0xffff97ca51b83480, >> > > > affinity = 0xffff97d03fffee60, >> > > > effective_affinity = 0xffff97d03fffe6c0 >> > > > }, >> > > > >> > > > crash> whatis cpumask_t >> > > > typedef struct cpumask { >> > > > unsigned long bits[128]; >> > > > } cpumask_t; >> > > > SIZE: 1024 >> > > > >> > > > In order to get the affinity, crash will read the memory range 0xffff97d03fffee60 >> > > > ~ 0xffff97d03fffee60 + 1024(0x400) by line: >> > > > >> > > > readmem(affinity_ptr, KVADDR, affinity, len, >> > > > "irq_desc affinity", FAULT_ON_ERROR); >> > > > >> > > > However the reading will exceed the effective memory range: >> > > > >> > > > crash> kmem 0xffff97d03fffee60 >> > > > CACHE OBJSIZE ALLOCATED TOTAL SLABS SSIZE NAME >> > > > ffff97c900044400 32 123297 162944 1273 4k kmalloc-32 >> > > > SLAB MEMORY NODE TOTAL ALLOCATED FREE >> > > > fffffca460ffff80 ffff97d03fffe000 3 128 81 47 >> > > > FREE / [ALLOCATED] >> > > > [ffff97d03fffee60] >> > > > >> > > > PAGE PHYSICAL MAPPING INDEX CNT FLAGS >> > > > fffffca460ffff80 83fffe000 dead000000000001 ffff97d03fffe340 1 d7ffffe0000800 slab >> > > > >> > > > crash> kmem ffff97d03ffff000 >> > > > PAGE PHYSICAL MAPPING INDEX CNT FLAGS >> > > > fffffca460ffffc0 83ffff000 0 0 1 d7ffffe0004000 reserved >> > > > >> > > > crash> dmesg >> > > > ... >> > > > [ 0.000000] BIOS-e820: [mem 0x00000000fe000000-0x00000000fe00ffff] reserved >> > > > [ 0.000000] BIOS-e820: [mem 0x0000000100000000-0x000000083fffefff] usable >> > > > [ 0.000000] BIOS-e820: [mem 0x000000083ffff000-0x000000083fffffff] reserved >> > > > ... >> > > > >> > > > The beginning physical address, aka 0x83fffe000, is located in the usable >> > > > area and is readable, however the later physical address, starting from >> > > > 0x83ffff000, is located in reserved region and not readable. In fact, >> > > > the affinity member is allocated by alloc_cpumask_var_node(), for the 192 CPUs >> > > > system, the allocated size is only 24, and we can see it is within >> > > > the kmalloc-32 slab. So it is incorrect to read 1024 length(given by >> > > > STRUCT_SIZE("cpumask_t")), only 24 is enough. >> > > > >> > > > Since there are plenty of places in crash which takes the value of >> > > > STRUCT_SIZE("cpumask_t"), and works fine for the past, this patch will >> > > > not modify them all, but only this place which encountered the issue. >> > > > >> > > > Signed-off-by: Tao Liu&lt;ltao(a)redhat.com&gt; >> > > > --- >> > > > kernel.c | 9 ++++++--- >> > > > 1 file changed, 6 insertions(+), 3 deletions(-) >> > > > >> > > > diff --git a/kernel.c b/kernel.c >> > > > index 8a9d498..464e877 100644 >> > > > --- a/kernel.c >> > > > +++ b/kernel.c >> > > > @@ -7362,7 +7362,7 @@ void >> > > > generic_get_irq_affinity(int irq) >> > > > { >> > > > ulong irq_desc_addr; >> > > > - long len; >> > > > + long len, len_cpumask; >> > > > ulong affinity_ptr; >> > > > ulong *affinity; >> > > > ulong tmp_addr; >> > > > @@ -7382,8 +7382,11 @@ generic_get_irq_affinity(int irq) >> > > > if (!action) >> > > > return; >> > > > >> > > > - if ((len = STRUCT_SIZE("cpumask_t")) < 0) >> > > > - len = DIV_ROUND_UP(kt->cpus, BITS_PER_LONG) * sizeof(ulong); >> > > > + len = DIV_ROUND_UP(kt->cpus, BITS_PER_LONG) * sizeof(ulong); >> > > > + len_cpumask = STRUCT_SIZE("cpumask_t"); >> > > > + if (len_cpumask > 0) { >> > > > + len = len_cpumask > len ? len : len_cpumask; >> > > > + } >> > > > >> > > >> > > This change looks good, but I still have two comments below: >> > > >> > > [1] Can we drop the evaluation of "STRUCT_SIZE("cpumask_t")" and just >> > > use the size of "DIV_ROUND_UP(kt->cpus, BITS_PER_LONG) * sizeof(ulong)" >> > > ? Are there any regression issues? >> >> I made a regression test, if all STRUCT_SIZE("cpumask_t") are replaced >> by DIV_ROUND_UP(...), there are regression issues found, but I didn't >> dive into the root cause of the failing reason. >> > > If so, let's keep it. > > Anyway, I'm still curious about the regression issue. > I re-read your comments, and I think I have misunderstood your request. The regressions are found when all places of STRUCT_SIZE("cpumask_t") in crash were replaced by DIV_ROUND_UP(...). You see there are plenty of places in crash which used STRUCT_SIZE("cpumask_t"), including the

2(the one which this patch is dealing with, and the one in tools.c) However if only the 2 places (the one which this patch is dealing with, and the one in tools.c) are replaced, there is no regression being noticed.

So I'm going to deal with the only 2 places in v2.

Thanks, Tao Liu >> > >> > I'm not sure about the change, I will run a regression against it. >> > > >> > > [2] There are the similar case in the get_cpumask_buf(), see tools.c, >> > > can you make the same change? >> >> Yes, unlike [1], with only the similar case modified, no regressions >> found. I will post v2 to include it. > > > Ok, sounds good. Thank you for the regression test. > > Lianbo > >> >> >> Thanks, >> Tao Liu >> >> > >> > Yes, I will give it a try to see if regressions are found. >> > >> > Thanks, >> > Tao Liu >> > > >> > > ulong * >> > > get_cpumask_buf(void) >> > > { >> > > int cpulen; >> > > if ((cpulen = STRUCT_SIZE("cpumask_t")) < 0) >> > > cpulen = DIV_ROUND_UP(kt->cpus, BITS_PER_LONG) * >> > > sizeof(ulong); >> > > return (ulong *)GETBUF(cpulen); >> > > } >> > > >> > > Any thoughts? >> > > >> > > >> > > Thanks >> > > >> > > Lianbo >> > > >> > > >> > > > affinity = (ulong *)GETBUF(len); >> > > > if (VALID_MEMBER(irq_common_data_affinity)) >> > > > -- 2.40.1 >> > > >>