From: Yi Yang yiyang13@huawei.com
stable inclusion from stable-v5.10.121 commit d787a57a17cf0e36cfd44659539c60fa18ce8c9d category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I5L6CQ
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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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 Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com Acked-by: Xie XiuQi xiexiuqi@huawei.com --- arch/xtensa/platforms/iss/simdisk.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-)
diff --git a/arch/xtensa/platforms/iss/simdisk.c b/arch/xtensa/platforms/iss/simdisk.c index 3447556d276d..2b3c829f655b 100644 --- a/arch/xtensa/platforms/iss/simdisk.c +++ b/arch/xtensa/platforms/iss/simdisk.c @@ -213,12 +213,18 @@ 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); }