habanalabs: fix debugfs code

This fixes multiple things in the habanalabs debugfs code, in particular:

 - mmu_write() was unnecessarily verbose, copying around between multiple
   buffers
 - mmu_write() could write a user-specified, unbounded amount of userspace
   memory into a kernel buffer (out-of-bounds write)
 - multiple debugfs read handlers ignored the user-supplied count,
   potentially corrupting out-of-bounds userspace data
 - hl_device_read() was unnecessarily verbose
 - hl_device_write() could read uninitialized stack memory
 - multiple debugfs read handlers copied terminating null characters to
   userspace

Signed-off-by: Jann Horn <jannh@google.com>
Reviewed-by: Oded Gabbay <oded.gabbay@gmail.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>
Cc: stable@vger.kernel.org

diff --git a/drivers/misc/habanalabs/debugfs.c b/drivers/misc/habanalabs/debugfs.c
index a444769..0ce5621 100644 (file)
--- a/drivers/misc/habanalabs/debugfs.c
+++ b/drivers/misc/habanalabs/debugfs.c
@@ -459,41 +459,31 @@ static ssize_t mmu_write(struct file *file, const char __user *buf,
        struct hl_debugfs_entry *entry = s->private;
        struct hl_dbg_device_entry *dev_entry = entry->dev_entry;
        struct hl_device *hdev = dev_entry->hdev;
-       char kbuf[MMU_KBUF_SIZE], asid_kbuf[MMU_ASID_BUF_SIZE],
-               addr_kbuf[MMU_ADDR_BUF_SIZE];
+       char kbuf[MMU_KBUF_SIZE];
        char *c;
        ssize_t rc;
 
        if (!hdev->mmu_enable)
                return count;
 
-       memset(kbuf, 0, sizeof(kbuf));
-       memset(asid_kbuf, 0, sizeof(asid_kbuf));
-       memset(addr_kbuf, 0, sizeof(addr_kbuf));
-
+       if (count > sizeof(kbuf) - 1)
+               goto err;
        if (copy_from_user(kbuf, buf, count))
                goto err;
-
-       kbuf[MMU_KBUF_SIZE - 1] = 0;
+       kbuf[count] = 0;
 
        c = strchr(kbuf, ' ');
        if (!c)
                goto err;
+       *c = '\0';
 
-       memcpy(asid_kbuf, kbuf, c - kbuf);
-
-       rc = kstrtouint(asid_kbuf, 10, &dev_entry->mmu_asid);
+       rc = kstrtouint(kbuf, 10, &dev_entry->mmu_asid);
        if (rc)
                goto err;
 
-       c = strstr(kbuf, " 0x");
-       if (!c)
+       if (strncmp(c+1, "0x", 2))
                goto err;
-
-       c += 3;
-       memcpy(addr_kbuf, c, (kbuf + count) - c);
-
-       rc = kstrtoull(addr_kbuf, 16, &dev_entry->mmu_addr);
+       rc = kstrtoull(c+3, 16, &dev_entry->mmu_addr);
        if (rc)
                goto err;
 
@@ -600,10 +590,8 @@ static ssize_t hl_data_read32(struct file *f, char __user *buf,
        }
 
        sprintf(tmp_buf, "0x%08x\n", val);
-       rc = simple_read_from_buffer(buf, strlen(tmp_buf) + 1, ppos, tmp_buf,
-                       strlen(tmp_buf) + 1);
-
-       return rc;
+       return simple_read_from_buffer(buf, count, ppos, tmp_buf,
+                       strlen(tmp_buf));
 }
 
 static ssize_t hl_data_write32(struct file *f, const char __user *buf,
@@ -645,7 +633,6 @@ static ssize_t hl_get_power_state(struct file *f, char __user *buf,
        struct hl_dbg_device_entry *entry = file_inode(f)->i_private;
        struct hl_device *hdev = entry->hdev;
        char tmp_buf[200];
-       ssize_t rc;
        int i;
 
        if (*ppos)
@@ -660,10 +647,8 @@ static ssize_t hl_get_power_state(struct file *f, char __user *buf,
 
        sprintf(tmp_buf,
                "current power state: %d\n1 - D0\n2 - D3hot\n3 - Unknown\n", i);
-       rc = simple_read_from_buffer(buf, strlen(tmp_buf) + 1, ppos, tmp_buf,
-                       strlen(tmp_buf) + 1);
-
-       return rc;
+       return simple_read_from_buffer(buf, count, ppos, tmp_buf,
+                       strlen(tmp_buf));
 }
 
 static ssize_t hl_set_power_state(struct file *f, const char __user *buf,
@@ -716,8 +701,8 @@ static ssize_t hl_i2c_data_read(struct file *f, char __user *buf,
        }
 
        sprintf(tmp_buf, "0x%02x\n", val);
-       rc = simple_read_from_buffer(buf, strlen(tmp_buf) + 1, ppos, tmp_buf,
-                       strlen(tmp_buf) + 1);
+       rc = simple_read_from_buffer(buf, count, ppos, tmp_buf,
+                       strlen(tmp_buf));
 
        return rc;
 }
@@ -806,18 +791,9 @@ static ssize_t hl_led2_write(struct file *f, const char __user *buf,
 static ssize_t hl_device_read(struct file *f, char __user *buf,
                                        size_t count, loff_t *ppos)
 {
-       char tmp_buf[200];
-       ssize_t rc;
-
-       if (*ppos)
-               return 0;
-
-       sprintf(tmp_buf,
-               "Valid values: disable, enable, suspend, resume, cpu_timeout\n");
-       rc = simple_read_from_buffer(buf, strlen(tmp_buf) + 1, ppos, tmp_buf,
-                       strlen(tmp_buf) + 1);
-
-       return rc;
+       static const char *help =
+               "Valid values: disable, enable, suspend, resume, cpu_timeout\n";
+       return simple_read_from_buffer(buf, count, ppos, help, strlen(help));
 }
 
 static ssize_t hl_device_write(struct file *f, const char __user *buf,
@@ -825,7 +801,7 @@ static ssize_t hl_device_write(struct file *f, const char __user *buf,
 {
        struct hl_dbg_device_entry *entry = file_inode(f)->i_private;
        struct hl_device *hdev = entry->hdev;
-       char data[30];
+       char data[30] = {0};
 
        /* don't allow partial writes */
        if (*ppos != 0)