speakup: Add spinlock in synth_direct_store

All operations with synth buffer should be protected,
as there are global pointers, which should be modified atomically.

Found by Linux Driver Verification project (linuxtesting.org)

Signed-off-by: Pavel Andrianov <andrianov@ispras.ru>
Acked-by: Vaishali Thakkar <vaishali.thakkar@oracle.com>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/speakup/kobjects.c b/drivers/staging/speakup/kobjects.c
index 528cbdc..7fedee3 100644 (file)
--- a/drivers/staging/speakup/kobjects.c
+++ b/drivers/staging/speakup/kobjects.c
@@ -411,11 +411,13 @@ static ssize_t synth_direct_store(struct kobject *kobj,
        int len;
        int bytes;
        const char *ptr = buf;
+       unsigned long flags;
 
        if (!synth)
                return -EPERM;
 
        len = strlen(buf);
+       spin_lock_irqsave(&speakup_info.spinlock, flags);
        while (len > 0) {
                bytes = min_t(size_t, len, 250);
                strncpy(tmp, ptr, bytes);
@@ -425,6 +427,7 @@ static ssize_t synth_direct_store(struct kobject *kobj,
                ptr += bytes;
                len -= bytes;
        }
+       spin_unlock_irqrestore(&speakup_info.spinlock, flags);
        return count;
 }