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author | Coly Li <colyli@suse.de> | 2019-06-10 06:13:34 +0800 |
---|---|---|
committer | Jens Axboe <axboe@kernel.dk> | 2019-06-13 03:09:14 -0600 |
commit | 31b90956b124240aa8c63250243ae1a53585c5e2 (patch) | |
tree | e85467cc2d47d0fec2c70e585797d32886dce7f4 /drivers/md/bcache/bset.h | |
parent | c326f846ebc2a30eca386b85dffba96e23803d81 (diff) | |
download | linux-stable-31b90956b124240aa8c63250243ae1a53585c5e2.tar.gz linux-stable-31b90956b124240aa8c63250243ae1a53585c5e2.tar.bz2 linux-stable-31b90956b124240aa8c63250243ae1a53585c5e2.zip |
bcache: fix stack corruption by PRECEDING_KEY()
Recently people report bcache code compiled with gcc9 is broken, one of
the buggy behavior I observe is that two adjacent 4KB I/Os should merge
into one but they don't. Finally it turns out to be a stack corruption
caused by macro PRECEDING_KEY().
See how PRECEDING_KEY() is defined in bset.h,
437 #define PRECEDING_KEY(_k) \
438 ({ \
439 struct bkey *_ret = NULL; \
440 \
441 if (KEY_INODE(_k) || KEY_OFFSET(_k)) { \
442 _ret = &KEY(KEY_INODE(_k), KEY_OFFSET(_k), 0); \
443 \
444 if (!_ret->low) \
445 _ret->high--; \
446 _ret->low--; \
447 } \
448 \
449 _ret; \
450 })
At line 442, _ret points to address of a on-stack variable combined by
KEY(), the life range of this on-stack variable is in line 442-446,
once _ret is returned to bch_btree_insert_key(), the returned address
points to an invalid stack address and this address is overwritten in
the following called bch_btree_iter_init(). Then argument 'search' of
bch_btree_iter_init() points to some address inside stackframe of
bch_btree_iter_init(), exact address depends on how the compiler
allocates stack space. Now the stack is corrupted.
Fixes: 0eacac22034c ("bcache: PRECEDING_KEY()")
Signed-off-by: Coly Li <colyli@suse.de>
Reviewed-by: Rolf Fokkens <rolf@rolffokkens.nl>
Reviewed-by: Pierre JUHEN <pierre.juhen@orange.fr>
Tested-by: Shenghui Wang <shhuiw@foxmail.com>
Tested-by: Pierre JUHEN <pierre.juhen@orange.fr>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Cc: Nix <nix@esperi.org.uk>
Cc: stable@vger.kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'drivers/md/bcache/bset.h')
-rw-r--r-- | drivers/md/bcache/bset.h | 34 |
1 files changed, 20 insertions, 14 deletions
diff --git a/drivers/md/bcache/bset.h b/drivers/md/bcache/bset.h index bac76aabca6d..c71365e7c1fa 100644 --- a/drivers/md/bcache/bset.h +++ b/drivers/md/bcache/bset.h @@ -434,20 +434,26 @@ static inline bool bch_cut_back(const struct bkey *where, struct bkey *k) return __bch_cut_back(where, k); } -#define PRECEDING_KEY(_k) \ -({ \ - struct bkey *_ret = NULL; \ - \ - if (KEY_INODE(_k) || KEY_OFFSET(_k)) { \ - _ret = &KEY(KEY_INODE(_k), KEY_OFFSET(_k), 0); \ - \ - if (!_ret->low) \ - _ret->high--; \ - _ret->low--; \ - } \ - \ - _ret; \ -}) +/* + * Pointer '*preceding_key_p' points to a memory object to store preceding + * key of k. If the preceding key does not exist, set '*preceding_key_p' to + * NULL. So the caller of preceding_key() needs to take care of memory + * which '*preceding_key_p' pointed to before calling preceding_key(). + * Currently the only caller of preceding_key() is bch_btree_insert_key(), + * and it points to an on-stack variable, so the memory release is handled + * by stackframe itself. + */ +static inline void preceding_key(struct bkey *k, struct bkey **preceding_key_p) +{ + if (KEY_INODE(k) || KEY_OFFSET(k)) { + (**preceding_key_p) = KEY(KEY_INODE(k), KEY_OFFSET(k), 0); + if (!(*preceding_key_p)->low) + (*preceding_key_p)->high--; + (*preceding_key_p)->low--; + } else { + (*preceding_key_p) = NULL; + } +} static inline bool bch_ptr_invalid(struct btree_keys *b, const struct bkey *k) { |