scsi: lpfc: Prevent lpfc_debugfs_lockstat_write() buffer overflow

A static code analysis tool flagged the possibility of buffer overflow when
using copy_from_user() for a debugfs entry.

Currently, it is possible that copy_from_user() copies more bytes than what
would fit in the mybuf char array.  Add a min() restriction check between
sizeof(mybuf) - 1 and nbytes passed from the userspace buffer to protect
against buffer overflow.

Link: https://lore.kernel.org/r/20230301231626.9621-2-justintee8345@gmail.com
Signed-off-by: Justin Tee <justin.tee@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/lpfc/lpfc_debugfs.c b/drivers/scsi/lpfc/lpfc_debugfs.c
index f5252e4..3e365e5 100644 (file)
--- a/drivers/scsi/lpfc/lpfc_debugfs.c
+++ b/drivers/scsi/lpfc/lpfc_debugfs.c
@@ -2157,10 +2157,13 @@ lpfc_debugfs_lockstat_write(struct file *file, const char __user *buf,
        char mybuf[64];
        char *pbuf;
        int i;
+       size_t bsize;
 
        memset(mybuf, 0, sizeof(mybuf));
 
-       if (copy_from_user(mybuf, buf, nbytes))
+       bsize = min(nbytes, (sizeof(mybuf) - 1));
+
+       if (copy_from_user(mybuf, buf, bsize))
                return -EFAULT;
        pbuf = &mybuf[0];
 
@@ -2181,7 +2184,7 @@ lpfc_debugfs_lockstat_write(struct file *file, const char __user *buf,
                        qp->lock_conflict.wq_access = 0;
                }
        }
-       return nbytes;
+       return bsize;
 }
 #endif