ext4: Fix handling of extended tv_sec
In ext4, the bottom two bits of {a,c,m}time_extra are used to extend the {a,c,m}time fields, deferring the year 2038 problem to the year 2446. When decoding these extended fields, for times whose bottom 32 bits would represent a negative number, sign extension causes the 64-bit extended timestamp to be negative as well, which is not what's intended. This patch corrects that issue, so that the only negative {a,c,m}times are those between 1901 and 1970 (as per 32-bit signed timestamps). Some older kernels might have written pre-1970 dates with 1,1 in the extra bits. This patch treats those incorrectly-encoded dates as pre-1970, instead of post-2311, until kernel 4.20 is released. Hopefully by then e2fsck will have fixed up the bad data. Also add a comment explaining the encoding of ext4's extra {a,c,m}time bits. Signed-off-by:David Turner <novalis@novalis.org> Signed-off-by:
Theodore Ts'o <tytso@mit.edu> Reported-by:
Mark Harris <mh8928@yahoo.com> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=23732 Cc: stable@vger.kernel.org
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