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xtensa/simdisk: fix proc_read_simdisk()

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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>
This commit is contained in:
Yi Yang 2022-05-10 16:05:33 +08:00 committed by Max Filippov
parent c6ab42b31f
commit b011946d03
1 changed files with 12 additions and 6 deletions
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18
arch/xtensa/platforms/iss/simdisk.c
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@ -211,12 +211,18 @@ static ssize_t proc_read_simdisk(struct file *file, char __user *buf,
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);
}