diff options
Diffstat (limited to '0003-cgroup-fix-css_task_iter-crash-on-CSS_TASK_ITER_PROC.patch')
| -rw-r--r-- | 0003-cgroup-fix-css_task_iter-crash-on-CSS_TASK_ITER_PROC.patch | 114 |
1 files changed, 114 insertions, 0 deletions
diff --git a/0003-cgroup-fix-css_task_iter-crash-on-CSS_TASK_ITER_PROC.patch b/0003-cgroup-fix-css_task_iter-crash-on-CSS_TASK_ITER_PROC.patch new file mode 100644 index 000000000000..80a09f9a5469 --- /dev/null +++ b/0003-cgroup-fix-css_task_iter-crash-on-CSS_TASK_ITER_PROC.patch @@ -0,0 +1,114 @@ +From a3c64fe9d978f3ee8f21fac5b410c63fe7cce725 Mon Sep 17 00:00:00 2001 +Message-Id: <a3c64fe9d978f3ee8f21fac5b410c63fe7cce725.1514245012.git.jan.steffens@gmail.com> +In-Reply-To: <b0bfa7c33cead5dd87267cfd4c29fda47dc1adc4.1514245012.git.jan.steffens@gmail.com> +References: <b0bfa7c33cead5dd87267cfd4c29fda47dc1adc4.1514245012.git.jan.steffens@gmail.com> +From: Tejun Heo <tj@kernel.org> +Date: Wed, 20 Dec 2017 07:09:19 -0800 +Subject: [PATCH 3/3] cgroup: fix css_task_iter crash on CSS_TASK_ITER_PROC + +While teaching css_task_iter to handle skipping over tasks which +aren't group leaders, bc2fb7ed089f ("cgroup: add @flags to +css_task_iter_start() and implement CSS_TASK_ITER_PROCS") introduced a +silly bug. + +CSS_TASK_ITER_PROCS is implemented by repeating +css_task_iter_advance() while the advanced cursor is pointing to a +non-leader thread. However, the cursor variable, @l, wasn't updated +when the iteration has to advance to the next css_set and the +following repetition would operate on the terminal @l from the +previous iteration which isn't pointing to a valid task leading to +oopses like the following or infinite looping. + + BUG: unable to handle kernel NULL pointer dereference at 0000000000000254 + IP: __task_pid_nr_ns+0xc7/0xf0 + PGD 0 P4D 0 + Oops: 0000 [#1] SMP + ... + CPU: 2 PID: 1 Comm: systemd Not tainted 4.14.4-200.fc26.x86_64 #1 + Hardware name: System manufacturer System Product Name/PRIME B350M-A, BIOS 3203 11/09/2017 + task: ffff88c4baee8000 task.stack: ffff96d5c3158000 + RIP: 0010:__task_pid_nr_ns+0xc7/0xf0 + RSP: 0018:ffff96d5c315bd50 EFLAGS: 00010206 + RAX: 0000000000000000 RBX: ffff88c4b68c6000 RCX: 0000000000000250 + RDX: ffffffffa5e47960 RSI: 0000000000000000 RDI: ffff88c490f6ab00 + RBP: ffff96d5c315bd50 R08: 0000000000001000 R09: 0000000000000005 + R10: ffff88c4be006b80 R11: ffff88c42f1b8004 R12: ffff96d5c315bf18 + R13: ffff88c42d7dd200 R14: ffff88c490f6a510 R15: ffff88c4b68c6000 + FS: 00007f9446f8ea00(0000) GS:ffff88c4be680000(0000) knlGS:0000000000000000 + CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 + CR2: 0000000000000254 CR3: 00000007f956f000 CR4: 00000000003406e0 + Call Trace: + cgroup_procs_show+0x19/0x30 + cgroup_seqfile_show+0x4c/0xb0 + kernfs_seq_show+0x21/0x30 + seq_read+0x2ec/0x3f0 + kernfs_fop_read+0x134/0x180 + __vfs_read+0x37/0x160 + ? security_file_permission+0x9b/0xc0 + vfs_read+0x8e/0x130 + SyS_read+0x55/0xc0 + entry_SYSCALL_64_fastpath+0x1a/0xa5 + RIP: 0033:0x7f94455f942d + RSP: 002b:00007ffe81ba2d00 EFLAGS: 00000293 ORIG_RAX: 0000000000000000 + RAX: ffffffffffffffda RBX: 00005574e2233f00 RCX: 00007f94455f942d + RDX: 0000000000001000 RSI: 00005574e2321a90 RDI: 000000000000002b + RBP: 0000000000000000 R08: 00005574e2321a90 R09: 00005574e231de60 + R10: 00007f94458c8b38 R11: 0000000000000293 R12: 00007f94458c8ae0 + R13: 00007ffe81ba3800 R14: 0000000000000000 R15: 00005574e2116560 + Code: 04 74 0e 89 f6 48 8d 04 76 48 8d 04 c5 f0 05 00 00 48 8b bf b8 05 00 00 48 01 c7 31 c0 48 8b 0f 48 85 c9 74 18 8b b2 30 08 00 00 <3b> 71 04 77 0d 48 c1 e6 05 48 01 f1 48 3b 51 38 74 09 5d c3 8b + RIP: __task_pid_nr_ns+0xc7/0xf0 RSP: ffff96d5c315bd50 + +Fix it by moving the initialization of the cursor below the repeat +label. While at it, rename it to @next for readability. + +Signed-off-by: Tejun Heo <tj@kernel.org> +Fixes: bc2fb7ed089f ("cgroup: add @flags to css_task_iter_start() and implement CSS_TASK_ITER_PROCS") +Cc: stable@vger.kernel.org # v4.14+ +Reported-by: Laura Abbott <labbott@redhat.com> +Reported-by: Bronek Kozicki <brok@incorrekt.com> +Reported-by: George Amanakis <gamanakis@gmail.com> +Signed-off-by: Tejun Heo <tj@kernel.org> +--- + kernel/cgroup/cgroup.c | 14 ++++++-------- + 1 file changed, 6 insertions(+), 8 deletions(-) + +diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c +index 44857278eb8aa6a2..030e4286f14c715e 100644 +--- a/kernel/cgroup/cgroup.c ++++ b/kernel/cgroup/cgroup.c +@@ -4059,26 +4059,24 @@ static void css_task_iter_advance_css_set(struct css_task_iter *it) + + static void css_task_iter_advance(struct css_task_iter *it) + { +- struct list_head *l = it->task_pos; ++ struct list_head *next; + + lockdep_assert_held(&css_set_lock); +- WARN_ON_ONCE(!l); +- + repeat: + /* + * Advance iterator to find next entry. cset->tasks is consumed + * first and then ->mg_tasks. After ->mg_tasks, we move onto the + * next cset. + */ +- l = l->next; ++ next = it->task_pos->next; + +- if (l == it->tasks_head) +- l = it->mg_tasks_head->next; ++ if (next == it->tasks_head) ++ next = it->mg_tasks_head->next; + +- if (l == it->mg_tasks_head) ++ if (next == it->mg_tasks_head) + css_task_iter_advance_css_set(it); + else +- it->task_pos = l; ++ it->task_pos = next; + + /* if PROCS, skip over tasks which aren't group leaders */ + if ((it->flags & CSS_TASK_ITER_PROCS) && it->task_pos && +-- +2.15.1 + |