[SRU][J/I/H/F][PATCH 0/1] Drop "UBUNTU: SAUCE: cachefiles: Page leaking in cachefiles_read_backing_file while vmscan is active"
andrea.righi at canonical.com
Tue Oct 19 10:33:07 UTC 2021
"UBUNTU: SAUCE: cachefiles: Page leaking in cachefiles_read_backing_file while
vmscan is active" has been applied to fix a page leaking issue.
However a slightly different fix has been applied upstream:
9a24ce5b66f9 ("cachefiles: Fix page leak in cachefiles_read_backing_file while vmscan is active")
Basically we are fixing the same issue in two different ways at the same time,
but even worse our patch an introduce a potential NULL pointer dereference: we
do a put_page(newpage) and set newpage = NULL in the main for() loop and then
we may do additional put_page(newpage) after the main for loop if
ret == -EEXIST, that would trigger the NULL pointer dereference.
No test case or reproducer is available at the moment, this issue has been
found simply by reviewing the code.
Drop the SAUCE patch and rely on the upstream fix.
If the analysis is not correct we may re-introduce a page leak in cachefiles
(NFS for example), but it seems unlikely to happen, since the upstream fix is
addressing the page leaking already.
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