On 3/20/19 2:35 PM, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
> Fix a number of complaints about feeding sizeof(dest) directly to
> strncpy. We do this by declaring the char arrays to be one larger
> than necessary and subtracting one, to ensure that we never overfill
> the buffer.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
> mkfs/xfs_mkfs.c | 13 +++++++++++--
> quota/edit.c | 9 ++++++---
> 2 files changed, 17 insertions(+), 5 deletions(-)
>
> diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
> index 9e1c6ec5..e87c692c 100644
> --- a/mkfs/xfs_mkfs.c
> +++ b/mkfs/xfs_mkfs.c
> @@ -3251,8 +3251,17 @@ finish_superblock_setup(
> struct xfs_mount *mp,
> struct xfs_sb *sbp)
> {
> - if (cfg->label)
> - strncpy(sbp->sb_fname, cfg->label, sizeof(sbp->sb_fname));
> + if (cfg->label) {
> + size_t label_len;
> +
> + /*
> + * Labels are null terminated unless the string fits exactly
> + * in the label field, so assume sb_fname is zeroed and then
> + * do a memcpy because the destination isn't a normal C string.
> + */
> + label_len = min(sizeof(sbp->sb_fname), strlen(cfg->label));
Heh, comparing this to the patch I wrote in <checks notes> December and never
sent *cough*, it seems like it might be wise to memset the whole thing to 0,
to be sure we're not leaking bytes here and there in a short label?
+ memset(sbp->sb_fname, 0, sizeof(sbp->sb_fname));
Although, I suppose the prior strncpy had the same issue... *shrug*
> + memcpy(sbp->sb_fname, cfg->label, label_len);
> + }
>
> sbp->sb_dblocks = cfg->dblocks;
> sbp->sb_rblocks = cfg->rtblocks;
> diff --git a/quota/edit.c b/quota/edit.c
> index b10a5b34..f9938b8a 100644
> --- a/quota/edit.c
> +++ b/quota/edit.c
> @@ -368,8 +368,7 @@ restore_file(
> uint type)
> {
> char buffer[512];
> - char devbuffer[512];
> - char *dev = NULL;
> + char dev[512];
> uint mask;
> int cnt;
> uint32_t id;
> @@ -377,7 +376,11 @@ restore_file(
>
> while (fgets(buffer, sizeof(buffer), fp) != NULL) {
> if (strncmp("fs = ", buffer, 5) == 0) {
> - dev = strncpy(devbuffer, buffer+5, sizeof(devbuffer));
> + /*
> + * Copy the device name to dev, strip off the trailing
> + * newline, and move on to the next line.
> + */
> + strncpy(dev, buffer + 5, sizeof(dev) - 1);
> dev[strlen(dev) - 1] = '\0';
> continue;
> }
Ok.
I had something in io/label.c: label_f() as well. Do you not get complaints
about strncpy(label, optarg, sizeof(label)); ?
I essentially did the same thing as for mkfs, though with my gratuitous
memset:
break;
case 's':
- strncpy(label, optarg, sizeof(label));
+ len = min(strlen(optarg), sizeof(label));
+ /* Kernel doesn't care about null termination */
+ memset(label, 0, sizeof(label));
+ memcpy(label, optarg, len);
break;
default:
