Subject: linux-next: build failure after merge of the kspp tree

From: Stephen Rothwell <[email-masked]>
Date: Tue, 25 Jan 2022 11:57:57 +1100

Hi all,

After merging the kspp tree, today's linux-next build (x86_64
allmodconfig) failed like this:

In file included from include/linux/string.h:253,
                 from include/linux/bitmap.h:11,
                 from include/linux/cpumask.h:12,
                 from arch/x86/include/asm/cpumask.h:5,
                 from arch/x86/include/asm/msr.h:11,
                 from arch/x86/include/asm/processor.h:22,
                 from arch/x86/include/asm/cpufeature.h:5,
                 from arch/x86/include/asm/thread_info.h:53,
                 from include/linux/thread_info.h:60,
                 from arch/x86/include/asm/preempt.h:7,
                 from include/linux/preempt.h:78,
                 from include/linux/spinlock.h:55,
                 from include/linux/wait.h:9,
                 from include/linux/mempool.h:8,
                 from include/linux/bio.h:8,
                 from fs/btrfs/ioctl.c:7:
In function 'fortify_memcpy_chk',
    inlined from 'btrfs_ioctl_encoded_write' at fs/btrfs/ioctl.c:5082:3:
include/linux/fortify-string.h:316:25: error: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror=attribute-warning]
  316 |                         __write_overflow_field(p_size_field, size);
      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/fortify-string.h:324:25: error: call to '__read_overflow2_field' declared with attribute warning: detected read beyond size of field (2nd parameter); maybe use struct_group()? [-Werror=attribute-warning]
  324 |                         __read_overflow2_field(q_size_field, size);
      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors

Caused by commit

  602670289b69 ("fortify: Detect struct member overflows in memcpy() at compile-time")

interacting with commit

  504e1ebb6316 ("btrfs: add BTRFS_IOC_ENCODED_WRITE")

from the btrfs tree.

I applied the following hack:

From: Stephen Rothwell <[email-masked]>
Date: Tue, 25 Jan 2022 11:47:17 +1100
Subject: [PATCH] fix up for "btrfs: add BTRFS_IOC_ENCODED_WRITE"

Signed-off-by: Stephen Rothwell <[email-masked]>
---
 fs/btrfs/ioctl.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 73ad918a05a9..d34620034f8e 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -5079,9 +5079,14 @@ static int btrfs_ioctl_encoded_write(struct file *file, void __user *argp,
 		}
 		args.iov = compat_ptr(args32.iov);
 		args.iovcnt = args32.iovcnt;
-		memcpy(&args.offset, &args32.offset,
-		       sizeof(args) -
-		       offsetof(struct btrfs_ioctl_encoded_io_args, offset));
+		args.offset = args32.offset;
+		args.flags = args32.flags;
+		args.len = args32.len;
+		args.unencoded_len = args32.unencoded_len;
+		args.unencoded_offset = args32.unencoded_offset;
+		args.compression = args32.compression;
+		args.encryption = args32.encryption;
+		memcpy(args.reserved, args32.reserved, sizeof(args.reserved));
 #else
 		return -ENOTTY;
 #endif
-- 
2.34.1

-- 
Cheers,
Stephen Rothwell