sysfs: upgrade OOB write by buggy .show hook into WARNing

Buggy .show hook will get just 1 line of dmesg:

	fill_read_buffer: ext4_attr_show+0x0/0x600 returned bad count

It may or may not oops later in some unrelated process.

But buggy .show hook most likely is corrupting random memory past sysfs
buffer therefore deserving more. WARN, make it more visible and let
QA machines panic earlier.

Also, delete useless cast -- "count" is >=0 at this point.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Reviewed-by: Danilo Krummrich <dakr@kernel.org>
Link: https://patch.msgid.link/3cc3e8c6-c6e8-4625-a88f-f5708b935dab@p183
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 5709cede1d75689b4f08772ffcc4aabc8ec66970..6b3a8f62fa89c590c30c09f14745e12351a9712a 100644 (file)
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -70,9 +70,8 @@ static int sysfs_kf_seq_show(struct seq_file *sf, void *v)
         * The code works fine with PAGE_SIZE return but it's likely to
         * indicate truncated result or overflow in normal use cases.
         */
-       if (count >= (ssize_t)PAGE_SIZE) {
-               printk("fill_read_buffer: %pS returned bad count\n",
-                               ops->show);
+       if (count >= PAGE_SIZE) {
+               WARN(1, "OOB write or bad count %zd at %pS\n", count, ops->show);
                /* Try to struggle along */
                count = PAGE_SIZE - 1;
        }