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authorFlorian Weimer <fweimer@redhat.com>2019-08-28 11:59:45 +0200
committerFlorian Weimer <fweimer@redhat.com>2019-08-28 11:59:45 +0200
commit61d3db428176d9d0822e4e680305fe34285edff2 (patch)
tree22ad4258b0d656bdf5ece29ade65a3e321a9a1b9 /nptl/forward.c
parent3a9d025fdd56f595ef9cb142486da4ee1b75281f (diff)
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login: pututxline could fail to overwrite existing entries [BZ #24902]
The internal_getut_r function updates the file_offset variable and
therefore must always update last_entry as well.

Previously, if pututxline could not upgrade the read lock to a
write lock, internal_getut_r would update file_offset only,
without updating last_entry, and a subsequent call would not
overwrite the existing utmpx entry at file_offset, instead
creating a new entry.  This has been observed to cause unbounded
file growth in high-load situations.

This commit removes the buffer argument to internal_getut_r and
updates the last_entry variable directly, along with file_offset.

Initially reported and fixed by Ondřej Lysoněk.

Reviewed-by: Gabriel F. T. Gomes <gabrielftg@linux.ibm.com>
Diffstat (limited to 'nptl/forward.c')
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