kernel/linux.git, branch v3.16.49

Linux 3.16.49

2017-10-12T14:28:25+00:00

dm: flush queued bios when process blocks to avoid deadlock

2017-10-12T14:28:23+00:00

commit d67a5f4b5947aba4bfe9a80a2b86079c215ca755 upstream. Commit df2cb6daa4 ("block: Avoid deadlocks with bio allocation by stacking drivers") created a workqueue for every bio set and code in bio_alloc_bioset() that tries to resolve some low-memory deadlocks by redirecting bios queued on current->bio_list to the workqueue if the system is low on memory. However other deadlocks (see below **) may happen, without any low memory condition, because generic_make_request is queuing bios to current->bio_list (rather than submitting them). ** the related dm-snapshot deadlock is detailed here: https://www.redhat.com/archives/dm-devel/2016-July/msg00065.html Fix this deadlock by redirecting any bios on current->bio_list to the bio_set's rescue workqueue on every schedule() call. Consequently, when the process blocks on a mutex, the bios queued on current->bio_list are dispatched to independent workqueus and they can complete without waiting for the mutex to be available. The structure blk_plug contains an entry cb_list and this list can contain arbitrary callback functions that are called when the process blocks. To implement this fix DM (ab)uses the onstack plug's cb_list interface to get its flush_current_bio_list() called at schedule() time. This fixes the snapshot deadlock - if the map method blocks, flush_current_bio_list() will be called and it redirects bios waiting on current->bio_list to appropriate workqueues. Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1267650 Depends-on: df2cb6daa4 ("block: Avoid deadlocks with bio allocation by stacking drivers") Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer Signed-off-by: Ben Hutchings

cpuset: PF_SPREAD_PAGE and PF_SPREAD_SLAB should be atomic flags

2017-10-12T14:28:22+00:00

commit 2ad654bc5e2b211e92f66da1d819e47d79a866f0 upstream. When we change cpuset.memory_spread_{page,slab}, cpuset will flip PF_SPREAD_{PAGE,SLAB} bit of tsk->flags for each task in that cpuset. This should be done using atomic bitops, but currently we don't, which is broken. Tetsuo reported a hard-to-reproduce kernel crash on RHEL6, which happened when one thread tried to clear PF_USED_MATH while at the same time another thread tried to flip PF_SPREAD_PAGE/PF_SPREAD_SLAB. They both operate on the same task. Here's the full report: https://lkml.org/lkml/2014/9/19/230 To fix this, we make PF_SPREAD_PAGE and PF_SPREAD_SLAB atomic flags. v4: - updated mm/slab.c. (Fengguang Wu) - updated Documentation. Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Miao Xie Cc: Kees Cook Fixes: 950592f7b991 ("cpusets: update tasks' page/slab spread flags in time") Reported-by: Tetsuo Handa Signed-off-by: Zefan Li Signed-off-by: Tejun Heo Signed-off-by: Ben Hutchings

sched: add macros to define bitops for task atomic flags

2017-10-12T14:28:22+00:00

commit e0e5070b20e01f0321f97db4e4e174f3f6b49e50 upstream. This will simplify code when we add new flags. v3: - Kees pointed out that no_new_privs should never be cleared, so we shouldn't define task_clear_no_new_privs(). we define 3 macros instead of a single one. v2: - updated scripts/tags.sh, suggested by Peter Cc: Ingo Molnar Cc: Miao Xie Cc: Tetsuo Handa Acked-by: Peter Zijlstra (Intel) Acked-by: Kees Cook Signed-off-by: Zefan Li Signed-off-by: Tejun Heo Signed-off-by: Ben Hutchings

sched: fix confusing PFA_NO_NEW_PRIVS constant

2017-10-12T14:28:22+00:00

commit a2b86f772227bcaf962c8b134f8d187046ac5f0e upstream. Commit 1d4457f99928 ("sched: move no_new_privs into new atomic flags") defined PFA_NO_NEW_PRIVS as hexadecimal value, but it is confusing because it is used as bit number. Redefine it as decimal bit number. Note this changes the bit position of PFA_NOW_NEW_PRIVS from 1 to 0. Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Miao Xie Signed-off-by: Tetsuo Handa Acked-by: Kees Cook [ lizf: slightly modified subject and changelog ] Signed-off-by: Zefan Li Signed-off-by: Tejun Heo Signed-off-by: Ben Hutchings

sched: move no_new_privs into new atomic flags

2017-10-12T14:28:22+00:00

commit 1d4457f99928a968767f6405b4a1f50845aa15fd upstream. Since seccomp transitions between threads requires updates to the no_new_privs flag to be atomic, the flag must be part of an atomic flag set. This moves the nnp flag into a separate task field, and introduces accessors. Signed-off-by: Kees Cook Reviewed-by: Oleg Nesterov Reviewed-by: Andy Lutomirski [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings

Fix match_prepath()

2017-10-12T14:28:22+00:00

commit cd8c42968ee651b69e00f8661caff32b0086e82d upstream. Incorrect return value for shares not using the prefix path means that we will never match superblocks for these shares. Fixes: commit c1d8b24d1819 ("Compare prepaths when comparing superblocks") Signed-off-by: Sachin Prabhu Reviewed-by: Pavel Shilovsky Signed-off-by: Steve French Cc: Aurélien Aptel Signed-off-by: Ben Hutchings

Fix regression which breaks DFS mounting

2017-10-12T14:28:21+00:00

commit d171356ff11ab1825e456dfb979755e01b3c54a1 upstream. Patch a6b5058 results in -EREMOTE returned by is_path_accessible() in cifs_mount() to be ignored which breaks DFS mounting. Signed-off-by: Sachin Prabhu Reviewed-by: Aurelien Aptel Signed-off-by: Steve French Signed-off-by: Ben Hutchings

Move check for prefix path to within cifs_get_root()

2017-10-12T14:28:21+00:00

commit 348c1bfa84dfc47da1f1234b7f2bf09fa798edea upstream. Signed-off-by: Sachin Prabhu Tested-by: Aurelien Aptel Signed-off-by: Steve French Signed-off-by: Ben Hutchings

Compare prepaths when comparing superblocks

2017-10-12T14:28:21+00:00

commit c1d8b24d18192764fe82067ec6aa8d4c3bf094e0 upstream. The patch fs/cifs: make share unaccessible at root level mountable makes use of prepaths when any component of the underlying path is inaccessible. When mounting 2 separate shares having different prepaths but are other wise similar in other respects, we end up sharing superblocks when we shouldn't be doing so. Signed-off-by: Sachin Prabhu Tested-by: Aurelien Aptel Signed-off-by: Steve French Signed-off-by: Ben Hutchings