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ntp: fix non privileged system time shifting

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The ADJ_SETOFFSET bit added in commit 094aa188 ("ntp: Add ADJ_SETOFFSET
mode bit") also introduced a way for any user to change the system time.
Sneaky or buggy calls to adjtimex() could set

    ADJ_OFFSET_SS_READ | ADJ_SETOFFSET

which would result in a successful call to timekeeping_inject_offset().
This patch fixes the issue by adding the capability check.

Signed-off-by: Richard Cochran <richard.cochran@omicron.at>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Richard Cochran
2011-04-04 08:31:23 -07:00
committed by Linus Torvalds
parent b3b896c73b
commit 4352d9d44b
1 changed files with 2 additions and 0 deletions
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2
kernel/time/ntp.c
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@@ -652,6 +652,8 @@ int do_adjtimex(struct timex *txc)
struct timespec delta; struct timespec delta;
delta.tv_sec = txc->time.tv_sec; delta.tv_sec = txc->time.tv_sec;
delta.tv_nsec = txc->time.tv_usec; delta.tv_nsec = txc->time.tv_usec;
if (!capable(CAP_SYS_TIME))
return -EPERM;
if (!(txc->modes & ADJ_NANO)) if (!(txc->modes & ADJ_NANO))
delta.tv_nsec *= 1000; delta.tv_nsec *= 1000;
result = timekeeping_inject_offset(&delta); result = timekeeping_inject_offset(&delta);