[PATCH 5.18 834/879] xtensa/simdisk: fix proc_read_simdisk()

Greg Kroah-Hartman
2022-06-08T01:08:55Z

From: Yi Yang <yiyang13@huawei.com>

commit b011946d039d66bbc7102137e98cc67e1356aa87 upstream.

The commit a69755b18774 ("xtensa simdisk: switch to proc_create_data()")
split read operation into two parts, first retrieving the path when it's
non-null and second retrieving the trailing '\n'. However when the path
is non-null the first simple_read_from_buffer updates ppos, and the
second simple_read_from_buffer returns 0 if ppos is greater than 1 (i.e.
almost always). As a result reading from that proc file is almost always
empty.

Fix it by making a temporary copy of the path with the trailing '\n' and
using simple_read_from_buffer on that copy.

Cc: stable@vger.kernel.org
Fixes: a69755b18774 ("xtensa simdisk: switch to proc_create_data()")
Signed-off-by: Yi Yang <yiyang13@huawei.com>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/xtensa/platforms/iss/simdisk.c | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)

--- a/arch/xtensa/platforms/iss/simdisk.c
+++ b/arch/xtensa/platforms/iss/simdisk.c
@@ -211,12 +211,18 @@ static ssize_t proc_read_simdisk(struct
struct simdisk *dev = pde_data(file_inode(file));
const char *s = dev->filename;
if (s) {
- ssize_t n = simple_read_from_buffer(buf, size, ppos,
- s, strlen(s));
- if (n < 0)
- return n;
- buf += n;
- size -= n;
+ ssize_t len = strlen(s);
+ char *temp = kmalloc(len + 2, GFP_KERNEL);
+
+ if (!temp)
+ return -ENOMEM;
+
+ len = scnprintf(temp, len + 2, "%s\n", s);
+ len = simple_read_from_buffer(buf, size, ppos,
+ temp, len);
+
+ kfree(temp);
+ return len;
}
return simple_read_from_buffer(buf, size, ppos, "\n", 1);
}