On 4/22/19 3:57 PM, Darrick J. Wong wrote:
> On Mon, Apr 22, 2019 at 03:48:03PM -0500, Eric Sandeen wrote:
>> On 4/22/19 10:45 AM, 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>
>>
>> Hm, you don't actually do what the changelog says, do you? No buffer
>> changes size in this patch.
>
> I'll change it to:
>
> "Fix a number of complaints about feeding sizeof(dest) directly to
> strncpy. We do this by feeding strncpy the length of the buffer minus
> one, having checked that the allocated space are long enough."
sounds good, I'll just fix that here.
>> And FWIW, neither of these was actually a real problem (fgets guarantees
>> a null in the string) but hey, whatever makes gcc happy I guess?
>>
>> (I think we lose a char in the quota array, but 511 chars ought to be
>> enough for anybody right?)
>
> Well... the quota one is reading lines straight out of a file, right?
> So that probably ought to be char buf[PATH_MAX + length of other junk in
> the line], though with the current lower limit now nobody's complained
> so maybe it's fine....
>
> --D
>
>> Patch seems fine, though.
>>
>>> ---
>>> 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 3e2ef92d..db3ad38e 100644
>>> --- a/mkfs/xfs_mkfs.c
>>> +++ b/mkfs/xfs_mkfs.c
>>> @@ -3270,8 +3270,17 @@ 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));
>>> + 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;
>>> }
>>>
>
