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authorTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>2018-04-04 13:53:07 +0300
committerAl Viro <viro@zeniv.linux.org.uk>2018-04-16 09:06:47 +0300
commit8e04944f0ea8b838399049bdcda920ab36ae3b04 (patch)
tree830ce2c35100627212caaf732396cafd7bfc1dc8 /include
parent4a3877c4cedd95543f8726b0a98743ed8db0c0fb (diff)
downloadlinux-8e04944f0ea8b838399049bdcda920ab36ae3b04.tar.xz
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')
-rw-r--r--include/linux/shrinker.h7
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