On Mon, Jul 2, 2018 at 11:30 AM, Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote: > On Fri, Jun 29, 2018 at 11:59 PM, <dmitry.torokhov@xxxxxxxxx> wrote: >> On Monday, June 25, 2018 at 5:43:02 AM UTC-7, Dmitry Vyukov wrote: >>> >>> On Tue, Jun 19, 2018 at 8:51 PM, Dmitry Torokhov >>> <dmitry....@xxxxxxxxx> wrote: >>> > On Thu, Jun 14, 2018 at 05:47:03AM -0700, syzbot wrote: >>> >> Hello, >>> >> >>> >> syzbot found the following crash on: >>> >> >>> >> HEAD commit: d2d741e5d189 kmsan: add initialization for shmem pages >>> >> git tree: https://github.com/google/kmsan.git/master >>> >> console output: >>> >> https://syzkaller.appspot.com/x/log.txt?x=1775bae7800000 >>> >> kernel config: >>> >> https://syzkaller.appspot.com/x/.config?x=48f9de3384bcd0f >>> >> dashboard link: >>> >> https://syzkaller.appspot.com/bug?extid=c382812c78d98ecd9fb8 >>> >> compiler: clang version 7.0.0 (trunk 329391) >>> >> syzkaller >>> >> repro:https://syzkaller.appspot.com/x/repro.syz?x=13b31ae7800000 >>> >> C reproducer: >>> >> https://syzkaller.appspot.com/x/repro.c?x=1733255b800000 >>> >> >>> >> IMPORTANT: if you fix the bug, please add the following tag to the >>> >> commit: >>> >> Reported-by: syzbot+c38281...@xxxxxxxxxxxxxxxxxxxxxxxxx >>> >> >>> >> RBP: 00000000006cb018 R08: 0000000000000001 R09: 00007ffe93080031 >>> >> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000004 >>> >> R13: ffffffffffffffff R14: 0000000000000000 R15: 0000000000000000 >>> >> ------------[ cut here ]------------ >>> >> input_alloc_absinfo(): kcalloc() failed? >>> >> WARNING: CPU: 1 PID: 4498 at drivers/input/input.c:487 >>> >> input_alloc_absinfo+0x183/0x190 drivers/input/input.c:487 >>> >> Kernel panic - not syncing: panic_on_warn set ... >>> > >>> > Hmm, so there is not really a problem as far as I am concerned. We do >>> > generate a warning if we can't allocate memory for absinfo, as this is >>> > really unexpected, but the case is handled properly by the callers so >>> > there is no reason for us to go belly up here. >>> >>> Note to myself: ping this bug when "include/asm-generic/bug.h: clarify >>> valid uses of WARN()" is fully merged. >> >> >> No, this warning will still be there even after the "clarifying" patch is >> merged. It does not check user inputs, it warns that the system is so low on >> memory that we could not allocate measly amount needed for absinfo. Treat it >> as you treat OOM warnings from kmalloc() itself. > > Hi Dmitry, > > kmalloc does not produce WARNING on OOM. The rule is not only about > invalid inputs, it's also about any transient conditions and "WARNING > only for kernel bugs". > > To put this in larger context, being able to distinguish kernel bugs > from non-bugs is a very important and practically useful capability, > which in particular enables systematic testing, but also makes things > simpler for all kernel users. There must be a very significant reason > to abandon this capability. What is that reason in this case? > > I also don't understand what is so special about this case. If we want > user message for kmalloc failures, kmalloc is the right place for such > warning, rather than a random call site out of thousands. Consider, > the allocation failure can happen on the very next or previous kmalloc > call, and user won't be warned. The rest of the kernel (including the > rest of input sybsystem) does not warn on allocation failures, so that > looks like what we need to do here as well. Or, if there is something > very special about this particular kmalloc call site, something that > makes it different from thousands of other call sites, why don't you > want to replace it with pr_err which would both give the diagnostics > but also not block systematic testing? Which looks like a win-win to > me. > > Thanks So, Dmitry, do you mind fixing this in the name of unblocking kernel testing? -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
