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7e934cf5ac
xas_for_each_marked() is using entry == NULL as a termination condition
of the iteration. When xas_for_each_marked() is used protected only by
RCU, this can however race with xas_store(xas, NULL) in the following
way:
TASK1 TASK2
page_cache_delete() find_get_pages_range_tag()
xas_for_each_marked()
xas_find_marked()
off = xas_find_chunk()
xas_store(&xas, NULL)
xas_init_marks(&xas);
...
rcu_assign_pointer(*slot, NULL);
entry = xa_entry(off);
And thus xas_for_each_marked() terminates prematurely possibly leading
to missed entries in the iteration (translating to missing writeback of
some pages or a similar problem).
If we find a NULL entry that has been marked, skip it (unless we're trying
to allocate an entry).
Reported-by: Jan Kara <jack@suse.cz>
CC: stable@vger.kernel.org
Fixes:
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|---|---|---|
| .. | ||
| generated | ||
| linux | ||
| .gitignore | ||
| benchmark.c | ||
| bitmap.c | ||
| idr-test.c | ||
| iteration_check_2.c | ||
| iteration_check.c | ||
| linux.c | ||
| main.c | ||
| Makefile | ||
| multiorder.c | ||
| regression1.c | ||
| regression2.c | ||
| regression3.c | ||
| regression4.c | ||
| regression.h | ||
| tag_check.c | ||
| test.c | ||
| test.h | ||
| xarray.c | ||