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| author | Miaohe Lin <linmiaohe@huawei.com> | 2021-02-24 12:07:05 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-02-24 13:38:32 -0800 |
| commit | 1d88433bb00853bed0c776b6ad9156855c127da0 (patch) | |
| tree | bb18ee45ffd9f622b81af7f0c2c2fefb715418da /mm/hugetlb.c | |
| parent | c78a7f3639932c48b4e1d329fc80fd26aa1a2fa3 (diff) | |
| download | lwn-1d88433bb00853bed0c776b6ad9156855c127da0.tar.gz lwn-1d88433bb00853bed0c776b6ad9156855c127da0.zip | |
mm/hugetlb: fix use after free when subpool max_hpages accounting is not enabled
If a hugetlbfs filesystem is created with the min_size option and
without the size option, used_hpages is always 0 and might lead to
release subpool prematurely because it indicates no pages are used now
while there might be.
In order to fix this issue, we should check used_hpages == 0 iff
max_hpages accounting is enabled. As max_hpages accounting should be
enabled in most common case, this is not worth a Cc stable.
[mike.kravetz@oracle.com: new changelog]
Link: https://lkml.kernel.org/r/20210126115510.53374-1-linmiaohe@huawei.com
Signed-off-by: Hongxiang Lou <louhongxiang@huawei.com>
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/hugetlb.c')
| -rw-r--r-- | mm/hugetlb.c | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 9b7fa72fa8fd..e8d39b0fe4bd 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -97,16 +97,26 @@ static inline void ClearPageHugeFreed(struct page *head) /* Forward declaration */ static int hugetlb_acct_memory(struct hstate *h, long delta); -static inline void unlock_or_release_subpool(struct hugepage_subpool *spool) +static inline bool subpool_is_free(struct hugepage_subpool *spool) { - bool free = (spool->count == 0) && (spool->used_hpages == 0); + if (spool->count) + return false; + if (spool->max_hpages != -1) + return spool->used_hpages == 0; + if (spool->min_hpages != -1) + return spool->rsv_hpages == spool->min_hpages; + return true; +} + +static inline void unlock_or_release_subpool(struct hugepage_subpool *spool) +{ spin_unlock(&spool->lock); /* If no pages are used, and no other handles to the subpool * remain, give up any reservations based on minimum size and * free the subpool */ - if (free) { + if (subpool_is_free(spool)) { if (spool->min_hpages != -1) hugetlb_acct_memory(spool->hstate, -spool->min_hpages); |