block: don't access bio->bi_error after bio_put()

Commit 4246a0b6 ("block: add a bi_error field to struct bio") has added a few
dereferences of 'bio' after a call to bio_put(). This causes use-after-frees
such as:

[521120.719695] BUG: KASan: use after free in dio_bio_complete+0x2b3/0x320 at addr ffff880f36b38714
[521120.720638] Read of size 4 by task mount.ocfs2/9644
[521120.721212] =============================================================================
[521120.722056] BUG kmalloc-256 (Not tainted): kasan: bad access detected
[521120.722968] -----------------------------------------------------------------------------
[521120.722968]
[521120.723915] Disabling lock debugging due to kernel taint
[521120.724539] INFO: Slab 0xffffea003cdace00 objects=32 used=25 fp=0xffff880f36b38600 flags=0x46fffff80004080
[521120.726037] INFO: Object 0xffff880f36b38700 @offset=1792 fp=0xffff880f36b38800
[521120.726037]
[521120.726974] Bytes b4 ffff880f36b386f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
[521120.727898] Object ffff880f36b38700: 00 88 b3 36 0f 88 ff ff 00 00 d8 de 0b 88 ff ff  ...6............
[521120.728822] Object ffff880f36b38710: 02 00 00 f0 00 00 00 00 00 00 00 00 00 00 00 00  ................
[521120.729705] Object ffff880f36b38720: 01 00 00 00 00 00 00 00 00 00 00 00 01 00 00 00  ................
[521120.730623] Object ffff880f36b38730: 00 00 00 00 00 00 00 00 01 00 00 00 00 02 00 00  ................
[521120.731621] Object ffff880f36b38740: 00 02 00 00 01 00 00 00 d0 f7 87 ad ff ff ff ff  ................
[521120.732776] Object ffff880f36b38750: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
[521120.733640] Object ffff880f36b38760: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
[521120.734508] Object ffff880f36b38770: 01 00 03 00 01 00 00 00 88 87 b3 36 0f 88 ff ff  ...........6....
[521120.735385] Object ffff880f36b38780: 00 73 22 ad 02 88 ff ff 40 13 e0 3c 00 ea ff ff  .s".....@..<....
[521120.736667] Object ffff880f36b38790: 00 02 00 00 00 04 00 00 00 00 00 00 00 00 00 00  ................
[521120.737596] Object ffff880f36b387a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
[521120.738524] Object ffff880f36b387b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
[521120.739388] Object ffff880f36b387c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
[521120.740277] Object ffff880f36b387d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
[521120.741187] Object ffff880f36b387e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
[521120.742233] Object ffff880f36b387f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
[521120.743229] CPU: 41 PID: 9644 Comm: mount.ocfs2 Tainted: G    B           4.2.0-rc6-next-20150810-sasha-00039-gf909086 #2420
[521120.744274]  ffff880f36b38000 ffff880d89c8f638 ffffffffb6e9ba8a ffff880101c0e5c0
[521120.745025]  ffff880d89c8f668 ffffffffad76a313 ffff880101c0e5c0 ffffea003cdace00
[521120.745908]  ffff880f36b38700 ffff880f36b38798 ffff880d89c8f690 ffffffffad772854
[521120.747063] Call Trace:
[521120.747520] dump_stack (lib/dump_stack.c:52)
[521120.748053] print_trailer (mm/slub.c:653)
[521120.748582] object_err (mm/slub.c:660)
[521120.749079] kasan_report_error (include/linux/kasan.h:20 mm/kasan/report.c:152 mm/kasan/report.c:194)
[521120.750834] __asan_report_load4_noabort (mm/kasan/report.c:250)
[521120.753580] dio_bio_complete (fs/direct-io.c:478)
[521120.755752] do_blockdev_direct_IO (fs/direct-io.c:494 fs/direct-io.c:1291)
[521120.759765] __blockdev_direct_IO (fs/direct-io.c:1322)
[521120.761658] blkdev_direct_IO (fs/block_dev.c:162)
[521120.762993] generic_file_read_iter (mm/filemap.c:1738)
[521120.767405] blkdev_read_iter (fs/block_dev.c:1649)
[521120.768556] __vfs_read (fs/read_write.c:423 fs/read_write.c:434)
[521120.772126] vfs_read (fs/read_write.c:454)
[521120.773118] SyS_pread64 (fs/read_write.c:607 fs/read_write.c:594)
[521120.776062] entry_SYSCALL_64_fastpath (arch/x86/entry/entry_64.S:186)
[521120.777375] Memory state around the buggy address:
[521120.778118]  ffff880f36b38600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[521120.779211]  ffff880f36b38680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[521120.780315] >ffff880f36b38700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[521120.781465]                          ^
[521120.782083]  ffff880f36b38780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[521120.783717]  ffff880f36b38800: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[521120.784818] ==================================================================

This patch fixes a few of those places that I caught while auditing the patch, but the
original patch should be audited further for more occurences of this issue since I'm
not too familiar with the code.

Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 744b80c608e55f549fdb73d7cd3d5a9c4f08f333..59da573cf994719c9eea162fbeb9357ab78c2d0b 100644 (file)
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -1102,6 +1102,7 @@ static void crypt_endio(struct bio *clone)
        struct dm_crypt_io *io = clone->bi_private;
        struct crypt_config *cc = io->cc;
        unsigned rw = bio_data_dir(clone);
+       int error;
 
        /*
         * free the processed pages
@@ -1109,15 +1110,16 @@ static void crypt_endio(struct bio *clone)
        if (rw == WRITE)
                crypt_free_buffer_pages(cc, clone);
 
+       error = clone->bi_error;
        bio_put(clone);
 
-       if (rw == READ && !clone->bi_error) {
+       if (rw == READ && !error) {
                kcryptd_queue_crypt(io);
                return;
        }
 
-       if (unlikely(clone->bi_error))
-               io->error = clone->bi_error;
+       if (unlikely(error))
+               io->error = error;
 
        crypt_dec_pending(io);
 }

diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c
index efc6659f9d6a6c651d925c24aa6cb73c4453ee07..c84714f70378967496faefed95822c4b5c4f86ab 100644 (file)
--- a/drivers/md/dm-io.c
+++ b/drivers/md/dm-io.c
@@ -138,6 +138,7 @@ static void endio(struct bio *bio)
 {
        struct io *io;
        unsigned region;
+       int error;
 
        if (bio->bi_error && bio_data_dir(bio) == READ)
                zero_fill_bio(bio);
@@ -147,9 +148,10 @@ static void endio(struct bio *bio)
         */
        retrieve_io_and_region_from_bio(bio, &io, &region);
 
+       error = bio->bi_error;
        bio_put(bio);
 
-       dec_count(io, region, bio->bi_error);
+       dec_count(io, region, error);
 }
 
 /*-----------------------------------------------------------------

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index e3d48775c9df1c8b2b18214eac651ae5ca5b6fdc..085db931aafc9a9eb8f61c12f657a5949667f84b 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -4756,6 +4756,7 @@ static void raid5_align_endio(struct bio *bi)
        struct mddev *mddev;
        struct r5conf *conf;
        struct md_rdev *rdev;
+       int error = bi->bi_error;
 
        bio_put(bi);
 
@@ -4766,7 +4767,7 @@ static void raid5_align_endio(struct bio *bi)
 
        rdev_dec_pending(rdev, conf->mddev);
 
-       if (!bi->bi_error) {
+       if (!error) {
                trace_block_bio_complete(bdev_get_queue(raid_bi->bi_bdev),
                                         raid_bi, 0);
                bio_endio(raid_bi);

diff --git a/fs/direct-io.c b/fs/direct-io.c
index e1639c8c14d5da48ab30a5cc93d085c924bb0a6c..818c647f36d36762ab421715c440e2b6295b4f30 100644 (file)
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -459,12 +459,14 @@ static int dio_bio_complete(struct dio *dio, struct bio *bio)
 {
        struct bio_vec *bvec;
        unsigned i;
+       int err;
 
        if (bio->bi_error)
                dio->io_error = -EIO;
 
        if (dio->is_async && dio->rw == READ) {
                bio_check_pages_dirty(bio);     /* transfers ownership */
+               err = bio->bi_error;
        } else {
                bio_for_each_segment_all(bvec, bio, i) {
                        struct page *page = bvec->bv_page;
@@ -473,9 +475,10 @@ static int dio_bio_complete(struct dio *dio, struct bio *bio)
                                set_page_dirty_lock(page);
                        page_cache_release(page);
                }
+               err = bio->bi_error;
                bio_put(bio);
        }
-       return bio->bi_error;
+       return err;
 }
 
 /*