Messages in this thread | | | From | Nick Terrell <> | Subject | Re: Possible bug for ZSTD kernel decompressing | Date | Mon, 31 Jan 2022 20:31:10 +0000 |
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> On Jan 27, 2022, at 8:53 PM, Feng Tang <feng.tang@intel.com> wrote: > > Hi All, > > Recently 0Day reported a 32bit i386 kernel decompression failure for my > patch [1], which essentially increase the kernel data section's size > from 19MB to 53MB, with error message: > > early console in setup code > early console in extract_kernel > input_data: 0x05077079 > input_len: 0x00f8a633 > output: 0x01000000 > output_len: 0x045c4328 > kernel_total_size: 0x05040000 > needed_size: 0x05040000 > > Decompressing Linux... > > ZSTD-compressed data is corrupt > > -- System haltedBUG: kernel hang in boot stage > > From debug, it is likely a problem of ZSTD decompression code, as when I > reverted my patch and hacked to increase the size of kernel data > section by 32MB, the same error will happen. > > Some other hints are: > * same i386 config with lz4 and xz algo can boot > * X86_64 + zstd also boots fine > > This could be reproduced by qemu cmd: > > qemu-system-i386 -machine pc -cpu host -enable-kvm -kernel bzImage -m 2048m -smp 4 -serial stdio --append "earlyprintk=ttyS0,115200 console=ttyS0,115200" > > i386 kernel config is attached, and the debug patch as below: > --- > diff --git a/init/main.c b/init/main.c > index 767ee2672176..873f40ddf96e 100644 > --- a/init/main.c > +++ b/init/main.c > @@ -162,6 +162,10 @@ static size_t initargs_offs; > static char *execute_command; > static char *ramdisk_execute_command = "/init"; > > +#define DT_SIZE 8192000 > +static unsigned long tbuf[DT_SIZE] = { 1, 2, 3, 4, }; > + > /* > * Used to generate warnings if static_key manipulation functions are used > * before jump_label_init is called. > @@ -690,6 +694,11 @@ noinline void __ref rest_init(void) > struct task_struct *tsk; > int pid; > > + unsigned long i, j; > + for (i = 0; i < DT_SIZE; i++) > + j += tbuf[i]; > + printk("j = 0x%x\n", j); > + > rcu_scheduler_starting(); > /* > * We need to spawn init first so that it obtains pid 1, however > > Please let me know if you need more info. > > [1.] https://lore.kernel.org/lkml/1627456900-42743-1-git-send-email-feng.tang@intel.com/
I've been unable to reproduce this issue using the provided patch + config based on Linux v5.17-rc2.
What version of Linux are you testing on? Zstd was updated in v5.16, so if you're not testing on v5.16 or later, can you please re-test on v5.17-rc2?
Best, Nick Terrell
> Thanks, > Feng > <i386_decompress_fail.config>
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