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Commit 3eb8ff08 authored by Bruce Ashfield's avatar Bruce Ashfield
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kernel: drop upstreamed patches in v5.14+


Signed-off-by: default avatarBruce Ashfield <bruce.ashfield@gmail.com>
parent 9122787a
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From ab49d2db98bdee2c8c6e17fb59ded9e5292b0f41 Mon Sep 17 00:00:00 2001
From: Paul Gortmaker <paul.gortmaker@windriver.com>
Date: Wed, 16 Jun 2021 08:51:57 -0400
Subject: [PATCH] cgroup1: fix leaked context root causing sporadic NULL deref
in LTP
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Richard reported sporadic (roughly one in 10 or so) null dereferences and
other strange behaviour for a set of automated LTP tests. Things like:
BUG: kernel NULL pointer dereference, address: 0000000000000008
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
Oops: 0000 [#1] PREEMPT SMP PTI
CPU: 0 PID: 1516 Comm: umount Not tainted 5.10.0-yocto-standard #1
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-48-gd9c812dda519-prebuilt.qemu.org 04/01/2014
RIP: 0010:kernfs_sop_show_path+0x1b/0x60
...or these others:
RIP: 0010:do_mkdirat+0x6a/0xf0
RIP: 0010:d_alloc_parallel+0x98/0x510
RIP: 0010:do_readlinkat+0x86/0x120
There were other less common instances of some kind of a general scribble
but the common theme was mount and cgroup and a dubious dentry triggering
the NULL dereference. I was only able to reproduce it under qemu by
replicating Richard's setup as closely as possible - I never did get it
to happen on bare metal, even while keeping everything else the same.
In commit 71d883c37e8d ("cgroup_do_mount(): massage calling conventions")
we see this as a part of the overall change:
--------------
struct cgroup_subsys *ss;
- struct dentry *dentry;
[...]
- dentry = cgroup_do_mount(&cgroup_fs_type, fc->sb_flags, root,
- CGROUP_SUPER_MAGIC, ns);
[...]
- if (percpu_ref_is_dying(&root->cgrp.self.refcnt)) {
- struct super_block *sb = dentry->d_sb;
- dput(dentry);
+ ret = cgroup_do_mount(fc, CGROUP_SUPER_MAGIC, ns);
+ if (!ret && percpu_ref_is_dying(&root->cgrp.self.refcnt)) {
+ struct super_block *sb = fc->root->d_sb;
+ dput(fc->root);
deactivate_locked_super(sb);
msleep(10);
return restart_syscall();
}
--------------
In changing from the local "*dentry" variable to using fc->root, we now
export/leave that dentry pointer in the file context after doing the dput()
in the unlikely "is_dying" case. With LTP doing a crazy amount of back to
back mount/unmount [testcases/bin/cgroup_regression_5_1.sh] the unlikely
becomes slightly likely and then bad things happen.
A fix would be to not leave the stale reference in fc->root as follows:
--------------
dput(fc->root);
+ fc->root = NULL;
deactivate_locked_super(sb);
--------------
...but then we are just open-coding a duplicate of fc_drop_locked() so we
simply use that instead.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Tejun Heo <tj@kernel.org>
Cc: Zefan Li <lizefan.x@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: stable@vger.kernel.org # v5.1+
Reported-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Fixes: 71d883c37e8d ("cgroup_do_mount(): massage calling conventions")
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
---
fs/internal.h | 1 -
include/linux/fs_context.h | 1 +
kernel/cgroup/cgroup-v1.c | 4 +---
3 files changed, 2 insertions(+), 4 deletions(-)
diff --git a/fs/internal.h b/fs/internal.h
index a7cd0f64faa4..5155f6ce95c7 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -64,7 +64,6 @@ extern void __init chrdev_init(void);
*/
extern const struct fs_context_operations legacy_fs_context_ops;
extern int parse_monolithic_mount_data(struct fs_context *, void *);
-extern void fc_drop_locked(struct fs_context *);
extern void vfs_clean_context(struct fs_context *fc);
extern int finish_clean_context(struct fs_context *fc);
diff --git a/include/linux/fs_context.h b/include/linux/fs_context.h
index 37e1e8f7f08d..5b44b0195a28 100644
--- a/include/linux/fs_context.h
+++ b/include/linux/fs_context.h
@@ -139,6 +139,7 @@ extern int vfs_parse_fs_string(struct fs_context *fc, const char *key,
extern int generic_parse_monolithic(struct fs_context *fc, void *data);
extern int vfs_get_tree(struct fs_context *fc);
extern void put_fs_context(struct fs_context *fc);
+extern void fc_drop_locked(struct fs_context *fc);
/*
* sget() wrappers to be called from the ->get_tree() op.
diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index a5751784ad74..5f7f893187f6 100644
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -1219,9 +1219,7 @@ int cgroup1_get_tree(struct fs_context *fc)
ret = cgroup_do_get_tree(fc);
if (!ret && percpu_ref_is_dying(&ctx->root->cgrp.self.refcnt)) {
- struct super_block *sb = fc->root->d_sb;
- dput(fc->root);
- deactivate_locked_super(sb);
+ fc_drop_locked(fc);
ret = 1;
}
--
2.19.1
......@@ -10,6 +10,5 @@ patch arm64-perf-fix-backtrace-for-AAPCS-with-FP-enabled.patch
patch defconfigs-drop-obselete-options.patch
patch arm64-perf-Fix-wrong-cast-that-may-cause-wrong-trunc.patch
patch net-dccp-make-it-depend-on-CONFIG_BROKEN-CVE-2020-16.patch
patch cgroup1-fix-leaked-context-root-causing-sporadic-NUL.patch
patch rcu-Fix-stall-warning-deadlock-due-to-non-release-of.patch
patch iwlwifi-select-MAC80211_LEDS-conditionally.patch
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