From 92d055879d510a1a51315301ea788445cd11aacb Mon Sep 17 00:00:00 2001 From: Lukas Czerner Date: Fri, 6 Aug 2021 11:58:16 +0200 Subject: [PATCH 40/46] libext2fs: fix unexpected NULL variable Content-Type: text/plain The ext2fs_check_mount_point() function can be called with mtpt being NULL as for example from ext2fs_check_if_mounted(). However in the is_swap_device condition we use the mtpt in strncpy without checking whether it is non-null first. This should not be a problem on linux since the previous attempt to open the device exclusively would have prevented us from ever reaching the problematic strncpy. However it's still a bug and can cause problems on other systems, fix it by conditioning strncpy on mtpt not being null. Signed-off-by: Lukas Czerner Signed-off-by: Theodore Ts'o --- lib/ext2fs/ismounted.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/lib/ext2fs/ismounted.c b/lib/ext2fs/ismounted.c index 46d330d9..c28475d4 100644 --- a/lib/ext2fs/ismounted.c +++ b/lib/ext2fs/ismounted.c @@ -393,7 +393,8 @@ errcode_t ext2fs_check_mount_point(const char *device, int *mount_flags, if (is_swap_device(device)) { *mount_flags = EXT2_MF_MOUNTED | EXT2_MF_SWAP; - strncpy(mtpt, "", mtlen); + if (mtpt) + strncpy(mtpt, "", mtlen); } else { #ifdef HAVE_SETMNTENT retval = check_mntent(device, mount_flags, mtpt, mtlen); -- 2.35.1