On 14/03/2020 10:23, Rafael J. Wysocki wrote:
> On Thursday, March 12, 2020 12:13:45 PM CET Colin King wrote:
>> From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
>>
>> Reading ACPI data on ARM64 at a non-aligned offset from
>> /sys/firmware/acpi/tables/data/BERT will cause a splat because
>> the data is I/O memory mapped and being read with just a memcpy.
>> Fix this by introducing an I/O variant of memory_read_from_buffer
>> and using I/O memory mapped copies instead.
>>
>> Fixes the following splat:
>>
>> [ 439.789355] Unable to handle kernel paging request at virtual address ffff800041ac0007
>> [ 439.797275] Mem abort info:
>> [ 439.800078] ESR = 0x96000021
>> [ 439.803131] EC = 0x25: DABT (current EL), IL = 32 bits
>> [ 439.808437] SET = 0, FnV = 0
>> [ 439.811486] EA = 0, S1PTW = 0
>> [ 439.814621] Data abort info:
>> [ 439.817489] ISV = 0, ISS = 0x00000021
>> [ 439.821319] CM = 0, WnR = 0
>> [ 439.824282] swapper pgtable: 4k pages, 48-bit VAs, pgdp=00000000817fc000
>> [ 439.830979] [ffff800041ac0007] pgd=000000bffcfff003, pud=0000009f27cee003, pmd=000000bf4b993003, pte=0068000080280703
>> [ 439.841584] Internal error: Oops: 96000021 [#1] SMP
>> [ 439.846449] Modules linked in: nls_iso8859_1 dm_multipath scsi_dh_rdac scsi_dh_emc scsi_dh_alua ipmi_ssif input_leds joydev ipmi_devintf ipmi_msghandler thunderx2_pmu sch_fq_codel ip_tables x_tables autofs4 btrfs zstd_compress raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor xor_neon raid6_pq libcrc32c raid1 raid0 multipath linear i2c_smbus ast i2c_algo_bit crct10dif_ce drm_vram_helper uas ttm ghash_ce drm_kms_helper sha2_ce syscopyarea sha256_arm64 qede sysfillrect mpt3sas sha1_ce sysimgblt fb_sys_fops raid_class qed drm scsi_transport_sas usb_storage ahci crc8 gpio_xlp i2c_xlp9xx hid_generic usbhid hid aes_neon_bs aes_neon_blk aes_ce_blk crypto_simd cryptd aes_ce_cipher
>> [ 439.908474] CPU: 2 PID: 3926 Comm: a.out Not tainted 5.4.0-14-generic #17-Ubuntu
>> [ 439.915855] Hardware name: To be filled by O.E.M. Saber/Saber, BIOS 0ACKL027 07/01/2019
>> [ 439.923844] pstate: 80400009 (Nzcv daif +PAN -UAO)
>> [ 439.928625] pc : __memcpy+0x90/0x180
>> [ 439.932192] lr : memory_read_from_buffer+0x64/0x88
>> [ 439.936968] sp : ffff8000350dbc70
>> [ 439.940270] x29: ffff8000350dbc70 x28: ffff009e9c444b00
>> [ 439.945568] x27: 0000000000000000 x26: 0000000000000000
>> [ 439.950866] x25: 0000000056000000 x24: ffff800041ac0000
>> [ 439.956164] x23: ffff009ea163f980 x22: 0000000000000007
>> [ 439.961462] x21: ffff8000350dbce8 x20: 000000000000000e
>> [ 439.966760] x19: 0000000000000007 x18: ffff8000112f64a8
>> [ 439.972058] x17: 0000000000000000 x16: 0000000000000000
>> [ 439.977355] x15: 0000000080280000 x14: ffff800041aed000
>> [ 439.982653] x13: ffff009ee9fa2840 x12: ffff800041ad1000
>> [ 439.987951] x11: ffff8000115e1360 x10: ffff8000115e1360
>> [ 439.993248] x9 : 0000000000010000 x8 : ffff800011ad2658
>> [ 439.998546] x7 : ffff800041ac0000 x6 : ffff009ea163f980
>> [ 440.003844] x5 : 0140000000000000 x4 : 0000000000010000
>> [ 440.009141] x3 : ffff800041ac0000 x2 : 0000000000000007
>> [ 440.014439] x1 : ffff800041ac0007 x0 : ffff009ea163f980
>> [ 440.019737] Call trace:
>> [ 440.022173] __memcpy+0x90/0x180
>> [ 440.025392] acpi_data_show+0x54/0x80
>> [ 440.029044] sysfs_kf_bin_read+0x6c/0xa8
>> [ 440.032954] kernfs_file_direct_read+0x90/0x2d0
>> [ 440.037470] kernfs_fop_read+0x68/0x78
>> [ 440.041210] __vfs_read+0x48/0x90
>> [ 440.044511] vfs_read+0xd0/0x1a0
>> [ 440.047726] ksys_read+0x78/0x100
>> [ 440.051028] __arm64_sys_read+0x24/0x30
>> [ 440.054852] el0_svc_common.constprop.0+0xdc/0x1d8
>> [ 440.059629] el0_svc_handler+0x34/0xa0
>> [ 440.063366] el0_svc+0x10/0x14
>> [ 440.066411] Code: 36180062 f8408423 f80084c3 36100062 (b8404423)
>> [ 440.072492] ---[ end trace 45fb374e8d2d800e ]---
>>
>> A simple reproducer is as follows:
>>
>> #include <sys/types.h>
>> #include <sys/stat.h>
>> #include <fcntl.h>
>> #include <unistd.h>
>> #include <stdio.h>
>> #include <string.h>
>>
>> int main(void)
>> {
>> int fd;
>> char buffer[7];
>> ssize_t n;
>>
>> fd = open("/sys/firmware/acpi/tables/data/BERT", O_RDONLY);
>> if (fd < 0) {
>> perror("open failed");
>> return -1;
>> }
>> do {
>> n = read(fd, buffer, sizeof(buffer));
>> } while (n > 0);
>>
>> return 0;
>> }
>>
>> BugLink: https://bugs.launchpad.net/bugs/1866772
>> Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
>> ---
>> drivers/acpi/sysfs.c | 2 +-
>> fs/libfs.c | 33 +++++++++++++++++++++++++++++++++
>> include/linux/string.h | 2 ++
>> 3 files changed, 36 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/acpi/sysfs.c b/drivers/acpi/sysfs.c
>> index c60d2c6d31d6..fb9e216cb8c0 100644
>> --- a/drivers/acpi/sysfs.c
>> +++ b/drivers/acpi/sysfs.c
>> @@ -446,7 +446,7 @@ static ssize_t acpi_data_show(struct file *filp, struct kobject *kobj,
>> base = acpi_os_map_memory(data_attr->addr, data_attr->attr.size);
>> if (!base)
>> return -ENOMEM;
>> - rc = memory_read_from_buffer(buf, count, &offset, base,
>> + rc = memory_read_from_io_buffer(buf, count, &offset, base,
>> data_attr->attr.size);
>> acpi_os_unmap_memory(base, data_attr->attr.size);
>>
>> diff --git a/fs/libfs.c b/fs/libfs.c
>> index c686bd9caac6..3e112c51ce7b 100644
>> --- a/fs/libfs.c
>> +++ b/fs/libfs.c
>> @@ -800,6 +800,39 @@ ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
>> }
>> EXPORT_SYMBOL(memory_read_from_buffer);
>>
>> +/**
>> + * memory_read_from_io_buffer - copy data from a io memory mapped buffer
>> + * @to: the kernel space buffer to read to
>> + * @count: the maximum number of bytes to read
>> + * @ppos: the current position in the buffer
>> + * @from: the buffer to read from
>> + * @available: the size of the buffer
>> + *
>> + * The memory_read_from_buffer() function reads up to @count bytes from the
>> + * io memory mappy buffer @from at offset @ppos into the kernel space address
>> + * starting at @to.
>> + *
>> + * On success, the number of bytes read is returned and the offset @ppos is
>> + * advanced by this number, or negative value is returned on error.
>> + **/
>> +ssize_t memory_read_from_io_buffer(void *to, size_t count, loff_t *ppos,
>> + const void *from, size_t available)
>> +{
>> + loff_t pos = *ppos;
>> +
>> + if (pos < 0)
>> + return -EINVAL;
>> + if (pos >= available)
>> + return 0;
>> + if (count > available - pos)
>> + count = available - pos;
>> + memcpy_fromio(to, from + pos, count);
>> + *ppos = pos + count;
>> +
>> + return count;
>> +}
>> +EXPORT_SYMBOL(memory_read_from_io_buffer);
>> +
>> /*
>> * Transaction based IO.
>> * The file expects a single write which triggers the transaction, and then
>> diff --git a/include/linux/string.h b/include/linux/string.h
>> index 6dfbb2efa815..0c6ec2aa3909 100644
>> --- a/include/linux/string.h
>> +++ b/include/linux/string.h
>> @@ -216,6 +216,8 @@ int bprintf(u32 *bin_buf, size_t size, const char *fmt, ...) __printf(3, 4);
>>
>> extern ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
>> const void *from, size_t available);
>> +extern ssize_t memory_read_from_io_buffer(void *to, size_t count, loff_t *ppos,
>> + const void *from, size_t available);
>>
>> int ptr_to_hashval(const void *ptr, unsigned long *hashval_out);
>>
>>
>
> Applied as 5.7 material, thanks!
>
>
>
>
Hi, what's the state of this patch, it got applied but I don't see it in
5.7, 5.8 or 5.8-rc3?
Colin
