On Wed, Apr 6, 2016 at 2:27 AM, Shaohua Li <shli@xxxxxx> wrote: > On Wed, Apr 06, 2016 at 01:44:06AM +0800, Ming Lei wrote: >> After arbitrary bio size is supported, the incoming bio may >> be very big. We have to split the bio into small bios so that >> each holds at most BIO_MAX_PAGES bvecs for safety reason, such >> as bio_clone(). >> >> This patch fixes the following kernel crash: >> >> > [ 172.660142] BUG: unable to handle kernel NULL pointer dereference at >> > 0000000000000028 >> > [ 172.660229] IP: [<ffffffff811e53b4>] bio_trim+0xf/0x2a >> > [ 172.660289] PGD 7faf3e067 PUD 7f9279067 PMD 0 >> > [ 172.660399] Oops: 0000 [#1] SMP >> > [...] >> > [ 172.664780] Call Trace: >> > [ 172.664813] [<ffffffffa007f3be>] ? raid1_make_request+0x2e8/0xad7 [raid1] >> > [ 172.664846] [<ffffffff811f07da>] ? blk_queue_split+0x377/0x3d4 >> > [ 172.664880] [<ffffffffa005fb5f>] ? md_make_request+0xf6/0x1e9 [md_mod] >> > [ 172.664912] [<ffffffff811eb860>] ? generic_make_request+0xb5/0x155 >> > [ 172.664947] [<ffffffffa0445c89>] ? prio_io+0x85/0x95 [bcache] >> > [ 172.664981] [<ffffffffa0448252>] ? register_cache_set+0x355/0x8d0 [bcache] >> > [ 172.665016] [<ffffffffa04497d3>] ? register_bcache+0x1006/0x1174 [bcache] >> >> Fixes: 54efd50(block: make generic_make_request handle arbitrarily sized bios) > > this bug is introduced by d2be537c3ba >> Reported-by: Sebastian Roesner <sroesner-kernelorg@xxxxxxxxxxxxxxxxx> >> Reported-by: Eric Wheeler <bcache@xxxxxxxxxxxxxxxxxx> >> Cc: stable@xxxxxxxxxxxxxxx (4.2+) >> Cc: Shaohua Li <shli@xxxxxx> >> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxxxxx> >> --- >> I can reproduce the issue and verify the fix by the following approach: >> - create one raid1 over two virtio-blk >> - build bcache device over the above raid1 and another cache device. >> - set cache mode as writeback >> - run random write over ext4 on the bcache device >> - then the crash can be triggered > > can you explain why this is better than my original patch? Shaohua, your patch is wrong, please see the following link: https://lkml.org/lkml/2016/3/30/893 Thanks, > -- > To unsubscribe from this list: send the line "unsubscribe linux-block" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html