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strscpy: zero any trailing garbage bytes in the destination 

It's possible that the destination can be shadowed in userspace
(as, for example, the perf buffers are now).  So we should take
care not to leak data that could be inspected by userspace.

Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
This commit is contained in:
Chris Metcalf 2015-10-06 12:37:41 -04:00
parent c753bf34c9
commit 990486c8af
1 changed files with 2 additions and 1 deletions
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3
lib/string.c
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@ -203,12 +203,13 @@ ssize_t strscpy(char *dest, const char *src, size_t count)
unsigned long c, data; unsigned long c, data;
c = *(unsigned long *)(src+res); c = *(unsigned long *)(src+res);
*(unsigned long *)(dest+res) = c;
if (has_zero(c, &data, &constants)) { if (has_zero(c, &data, &constants)) {
data = prep_zero_mask(c, data, &constants); data = prep_zero_mask(c, data, &constants);
data = create_zero_mask(data); data = create_zero_mask(data);
*(unsigned long *)(dest+res) = c & zero_bytemask(data);
return res + find_zero(data); return res + find_zero(data);
} }
*(unsigned long *)(dest+res) = c;
res += sizeof(unsigned long); res += sizeof(unsigned long);
count -= sizeof(unsigned long); count -= sizeof(unsigned long);
max -= sizeof(unsigned long); max -= sizeof(unsigned long);