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| author |   Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> | 2018-04-04 19:53:07 +0900 |
|---|---|---|
| committer |   Al Viro <viro@zeniv.linux.org.uk> | 2018-04-16 02:06:47 -0400 |
| commit | 8e04944f0ea8b838399049bdcda920ab36ae3b04 (patch) | |
| tree | 830ce2c35100627212caaf732396cafd7bfc1dc8 /include/linux/shrinker.h | |
| parent | rpc_pipefs: fix double-dput() (diff) | |
| download | linux-dev-8e04944f0ea8b838399049bdcda920ab36ae3b04.tar.xz linux-dev-8e04944f0ea8b838399049bdcda920ab36ae3b04.zip | |
mm,vmscan: Allow preallocating memory for register_shrinker().
syzbot is catching so many bugs triggered by commit 9ee332d99e4d5a97
("sget(): handle failures of register_shrinker()"). That commit expected
that calling kill_sb() from deactivate_locked_super() without successful
fill_super() is safe, but the reality was different; some callers assign
attributes which are needed for kill_sb() after sget() succeeds.
For example, [1] is a report where sb->s_mode (which seems to be either
FMODE_READ | FMODE_EXCL | FMODE_WRITE or FMODE_READ | FMODE_EXCL) is not
assigned unless sget() succeeds. But it does not worth complicate sget()
so that register_shrinker() failure path can safely call
kill_block_super() via kill_sb(). Making alloc_super() fail if memory
allocation for register_shrinker() failed is much simpler. Let's avoid
calling deactivate_locked_super() from sget_userns() by preallocating
memory for the shrinker and making register_shrinker() in sget_userns()
never fail.
[1] https://syzkaller.appspot.com/bug?id=588996a25a2587be2e3a54e8646728fb9cae44e7
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reported-by: syzbot <syzbot+5a170e19c963a2e0df79@syzkaller.appspotmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'include/linux/shrinker.h')
| -rw-r--r-- | include/linux/shrinker.h | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h index 388ff2936a87..6794490f25b2 100644 --- a/include/linux/shrinker.h +++ b/include/linux/shrinker.h @@ -75,6 +75,9 @@ struct shrinker { #define SHRINKER_NUMA_AWARE (1 << 0) #define SHRINKER_MEMCG_AWARE (1 << 1) -extern int register_shrinker(struct shrinker *); -extern void unregister_shrinker(struct shrinker *); +extern int prealloc_shrinker(struct shrinker *shrinker); +extern void register_shrinker_prepared(struct shrinker *shrinker); +extern int register_shrinker(struct shrinker *shrinker); +extern void unregister_shrinker(struct shrinker *shrinker); +extern void free_prealloced_shrinker(struct shrinker *shrinker); #endif |