Re: [PATCH] f2fs: Replace strncpy with memcpy

From: Guenter Roeck
Date: Sun Jul 01 2018 - 22:16:48 EST


On 07/01/2018 06:53 PM, Chao Yu wrote:
On 2018/7/2 4:57, Guenter Roeck wrote:
gcc 8.1.0 complains:

fs/f2fs/namei.c: In function 'f2fs_update_extension_list':
fs/f2fs/namei.c:257:3: warning:
'strncpy' output truncated before terminating nul copying
as many bytes from a string as its length
fs/f2fs/namei.c:249:3: warning:
'strncpy' output truncated before terminating nul copying
as many bytes from a string as its length

Using strncpy() is indeed less than perfect since the length of data to
be copied has already been determined with strlen(). Replace strncpy()
with memcpy() to address the warning and optimize the code a little.

Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
---
fs/f2fs/namei.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
index 231b7f3ea7d3..e75607544f7c 100644
--- a/fs/f2fs/namei.c
+++ b/fs/f2fs/namei.c
@@ -246,7 +246,7 @@ int f2fs_update_extension_list(struct f2fs_sb_info *sbi, const char *name,
return -EINVAL;
if (hot) {
- strncpy(extlist[count], name, strlen(name));
+ memcpy(extlist[count], name, strlen(name));

How about replacing with strcpy(extlist[count], name)? Because name length has
already been checked before f2fs_update_extension_list, it should be valid, and
will not cause overflow during copying.


Your call; feel free to submit an alternative. Since it is different files, static
analysis might not know and complain, though. You might want to make sure that this
doesn't happen, and also add a comment explaining the reason for using strcpy().

Thanks,
Guenter