[RFC] linux 3.4 BUG on lib/prio_tree.c:280!

From: Yisheng Xie
Date: Wed Apr 11 2018 - 05:35:10 EST

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Hi all,

We meet a problem with linux 3.4, which trigger BUG on lib/prio_tree.c:280!

kernel BUG at /usr/src/packages/BUILD/kernel-default-3.4.24.25/linux-3.4/lib/prio_tree.c:280!
[...]
Process: grep (pid: 64867, threadinfo: ffff880005010000, task: ffff8800022d5c80) on CPU: 2
Pid: 64867, comm: grep
RIP: 0010:[<ffffffff812259c9>] [<ffffffff812259c9>] prio_tree_remove+0xe9/0xf0
RSP: 0018:ffff880005011d00 EFLAGS: 00010283
RAX: ffff880001eb6650 RBX: ffff880001eb6650 RCX: ffff88013d0ecb38
RDX: ffff88013d0ecb00 RSI: ffff880001eb6650 RDI: ffff88013d0ecb38
RBP: ffff880005011d38 R08: 2222222222222222 R09: 2222222222222222
R10: 0000000000000000 R11: 0000000000000000 R12: ffff88013d0ecb38
R13: ffff880001eb6650 R14: ffff88013d0ecb00 R15: ffff880001eb6600
FS: 00007f366dd35700(0000) GS:ffff88016d840000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000402008 CR3: 000000000ac65000 CR4: 00000000001607f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
[<ffffffff8110476b>] vma_prio_tree_remove+0x9b/0x130
[<ffffffff81114efb>] __remove_shared_vm_struct.isra.27+0x3b/0x60
[<ffffffff811153f9>] unlink_file_vma+0x49/0x70
[<ffffffff8110e5f1>] free_pgtables+0x41/0x120
[<ffffffff81115102>] unmap_region+0xe2/0x140
[<ffffffff811163b6>] do_munmap+0x2f6/0x3d0
[<ffffffff811164dc>] vm_munmap+0x4c/0x70
[<ffffffff81117bc6>] sys_munmap+0x26/0x40
[<ffffffff81467965>] system_call_fastpath+0x16/0x1b

we have checked the vmcore, and find the vma was added to a prio tree which is no
belong to its present vma->vm_file->f_mapping->i_mmap, but I do not know how this
could happen, any clue about this?

I know maybe it is not suitable to discuss a problem for this old kernel here, but
do hope to get some help from some more specialist. Thanks for any of comment.

Thanks
Yisheng

The more detail steps I debug as following:
crash> dis -l prio_tree_remove
[...]
and find r13 is node, rbx is the cur, (r13 is the same as rbx, so cur is the same as node)
for cur we get its vma:

crash> struct -x vm_area_struct 0xffff880001eb6600
struct vm_area_struct {
vm_mm = 0xffff880004f04400,
vm_start = 0x7f366dd37000,
vm_end = 0x7f366dd3d000,
vm_next = 0x0,
vm_prev = 0x0,
vm_page_prot = {
pgprot = 0x8000000000000025
},
vm_flags = 0x8000071,
vm_rb = {
rb_parent_color = 0xffff880001eb7d79,
rb_right = 0x0,
rb_left = 0xffff880001eb73b8
},
shared = {
vm_set = {
list = {
next = 0xffff880001eb6650,
prev = 0xffff880001eb6650
},
parent = 0xffff880001eb6650,
head = 0xffff8800096da000
},
prio_tree_node = {
left = 0xffff880001eb6650,
right = 0xffff880001eb6650,
parent = 0xffff880001eb6650
}
},
anon_vma_chain = {
next = 0xffff880001eb6670,
prev = 0xffff880001eb6670
},
anon_vma = 0x0,
vm_ops = 0xffffffff81614640,
vm_pgoff = 0x0,
vm_file = 0xffff880036c5c700,
vm_private_data = 0x0,
vm_policy = 0x0,
euler_kabi_padding = {0x0, 0x0}
}

then file and dentry:
crash> struct -x file 0xffff880036c5c700
struct file {
f_u = {
fu_list_deprecated = {
next = 0x0,
prev = 0x0
},
fu_rcuhead = {
next = 0x0,
func = 0
}
},
f_path = {
mnt = 0xffff8801550b82a0,
dentry = 0xffff88013f531368
},
f_op = 0xffffffff81614480,
f_lock = {
{
rlock = {
raw_lock = {
{
head_tail = 0x0,
tickets = {
head = 0x0,
tail = 0x0
}
}
},
magic = 0xdead4ead,
owner_cpu = 0xffffffff,
owner = 0xffffffffffffffff
}
}
},
f_sb_list_cpu_deprecated = 0x0,
f_count = {
counter = 0x4
},
f_flags = 0x8000,
f_mode = 0x1d,
f_pos = 0x340,
f_owner = {
lock = {
raw_lock = {
lock = 0x100000,
write = 0x100000
},
magic = 0xdeaf1eed,
owner_cpu = 0xffffffff,
owner = 0xffffffffffffffff
},
pid = 0x0,
pid_type = PIDTYPE_PID,
uid = 0x0,
euid = 0x0,
signum = 0x0
},
f_cred = 0xffff88000ac2ccc0,
f_ra = {
start = 0x0,
size = 0x0,
async_size = 0x0,
ra_pages = 0x0,
mmap_miss = 0x0,
prev_pos = 0xffffffffffffffff
},
f_version = 0x0,
f_security = 0x0,
private_data = 0x0,
f_ep_links = {
next = 0xffff880036c5c7d0,
prev = 0xffff880036c5c7d0
},
f_tfile_llink = {
next = 0xffff880036c5c7e0,
prev = 0xffff880036c5c7e0
},
f_mapping = 0xffff88013d0ecb00
}

crash> struct -x dentry 0xffff88013f531368
struct dentry {
d_flags = 0x88,
d_seq = {
sequence = 0x4
},
d_hash = {
next = 0x0,
pprev = 0xffffc9000233bec8
},
d_parent = 0xffff88013f573e60,
d_name = {
hash = 0x67491608,
len = 0xe,
name = 0xffff88013f5313a0 "libc-2.11.3.so"
},
d_inode = 0xffff88013d0ec980,
d_iname = "libc-2.11.3.so\000lect_nvram.sh\000\000\000",
d_count = 0x4f,
d_lock = {
{
rlock = {
raw_lock = {
{
head_tail = 0x7878,
tickets = {
head = 0x78,
tail = 0x78
}
}
},
magic = 0xdead4ead,
owner_cpu = 0xffffffff,
owner = 0xffffffffffffffff
}
}
},
d_op = 0xffffffff81618f80,
d_sb = 0xffff88016d411800,
d_time = 0x0,
d_fsdata = 0x0,
d_lru = {
next = 0xffff88013f531400,
prev = 0xffff88013f531400
},
d_child = {
next = 0xffff88013f525c80,
prev = 0xffff88013f524f00
},
d_subdirs = {
next = 0xffff88013f531420,
prev = 0xffff88013f531420
},
d_u = {
d_alias = {
next = 0xffff88013d0ecac8,
prev = 0xffff88013d0ecac8
},
d_rcu = {
next = 0xffff88013d0ecac8,
func = 0xffff88013d0ecac8
}
}
}

ok, go back to vma itself find it has head, and the head is another vma: 0xffff8800096da000;
crash> struct -x vm_area_struct 0xffff8800096da000
struct vm_area_struct {
vm_mm = 0xffff880073fbbc00,
vm_start = 0x7f555fc20000,
vm_end = 0x7f555fc26000,
vm_next = 0xffff8800096dba40,
vm_prev = 0xffff8800096dacc0,
vm_page_prot = {
pgprot = 0x8000000000000025
},
vm_flags = 0x8000071,
vm_rb = {
rb_parent_color = 0xffff8800096dba78,
rb_right = 0x0,
rb_left = 0x0
},
shared = {
vm_set = {
list = {
next = 0xffff880002477910,
prev = 0xffff88002499cc50
},
parent = 0x0,
head = 0xffff880001eb6600
},
prio_tree_node = {
left = 0xffff880002477910,
right = 0xffff88002499cc50,
parent = 0x0
}
},
anon_vma_chain = {
next = 0xffff8800096da070,
prev = 0xffff8800096da070
},
anon_vma = 0x0,
vm_ops = 0xffffffff81614640,
vm_pgoff = 0x0,
vm_file = 0xffff880039facb00,
vm_private_data = 0x0,
vm_policy = 0x0,
euler_kabi_padding = {0x0, 0x0}
}

Then file and dentry:

crash> struct -x file 0xffff880039facb00
struct file {
f_u = {
fu_list_deprecated = {
next = 0x0,
prev = 0x0
},
fu_rcuhead = {
next = 0x0,
func = 0
}
},
f_path = {
mnt = 0xffff8801550b82a0,
dentry = 0xffff880056495290
},
f_op = 0xffffffff81614480,
f_lock = {
{
rlock = {
raw_lock = {
{
head_tail = 0x0,
tickets = {
head = 0x0,
tail = 0x0
}
}
},
magic = 0xdead4ead,
owner_cpu = 0xffffffff,
owner = 0xffffffffffffffff
}
}
},
f_sb_list_cpu_deprecated = 0x0,
f_count = {
counter = 0x1
},
f_flags = 0x8000,
f_mode = 0x1d,
f_pos = 0x0,
f_owner = {
lock = {
raw_lock = {
lock = 0x100000,
write = 0x100000
},
magic = 0xdeaf1eed,
owner_cpu = 0xffffffff,
owner = 0xffffffffffffffff
},
pid = 0x0,
pid_type = PIDTYPE_PID,
uid = 0x0,
euid = 0x0,
signum = 0x0
},
f_cred = 0xffff880002477980,
f_ra = {
start = 0x0,
size = 0x0,
async_size = 0x0,
ra_pages = 0x0,
mmap_miss = 0x0,
prev_pos = 0xffffffffffffffff
},
f_version = 0x0,
f_security = 0x0,
private_data = 0x0,
f_ep_links = {
next = 0xffff880039facbd0,
prev = 0xffff880039facbd0
},
f_tfile_llink = {
next = 0xffff880039facbe0,
prev = 0xffff880039facbe0
},
f_mapping = 0xffff88013d235b90 ----> oh, no the same address_space
}

Check this address_space:
crash> struct -x address_space 0xffff88013d235b90
struct address_space {
host = 0xffff88013d235a10,
page_tree = {
height = 0x1,
gfp_mask = 0x20,
rnode = 0xffff88011b9ff599
},
tree_lock = {
{
rlock = {
raw_lock = {
{
head_tail = 0x2a2a,
tickets = {
head = 0x2a,
tail = 0x2a
}
}
},
magic = 0xdead4ead,
owner_cpu = 0xffffffff,
owner = 0xffffffffffffffff
}
}
},
i_mmap_writable = 0x0,
i_mmap = {
prio_tree_node = 0xffff880001eb6650, -----> this is rbx(cur and also the node)
index_bits = 0x3,
raw = 0x1
},
i_mmap_nonlinear = {
next = 0xffff88013d235bd8,
prev = 0xffff88013d235bd8
},
i_mmap_mutex = {
count = {
counter = 0x1
},
wait_lock = {
{
rlock = {
raw_lock = {
{
head_tail = 0x8f8f,
tickets = {
head = 0x8f,
tail = 0x8f
}
}
},
magic = 0xdead4ead,
owner_cpu = 0xffffffff,
owner = 0xffffffffffffffff
}
}
},
wait_list = {
next = 0xffff88013d235c08,
prev = 0xffff88013d235c08
},
owner = 0xffff88004cfec560,
name = 0x0,
magic = 0xffff88013d235be8
},
nrpages = 0x6,
writeback_index = 0x0,
a_ops = 0xffffffff81614240,
flags = 0x200da,
backing_dev_info = 0xffffffff818890e0,
private_lock = {
{
rlock = {
raw_lock = {
{
head_tail = 0x0,
tickets = {
head = 0x0,
tail = 0x0
}
}
},
magic = 0xdead4ead,
owner_cpu = 0xffffffff,
owner = 0xffffffffffffffff
}
}
},
private_list = {
next = 0xffff88013d235c70,
prev = 0xffff88013d235c70
},
assoc_mapping = 0x0
}
crash> struct dentry -x 0xffff880056495290
struct dentry {
d_flags = 0x88,
d_seq = {
sequence = 0x8
},
d_hash = {
next = 0x0,
pprev = 0xffffc900000bf508
},
d_parent = 0xffff88013f79e288,
d_name = {
hash = 0x7983921a,
len = 0xb,
name = 0xffff8800564952c8 "ld.so.cache"
},
d_inode = 0xffff88013d235a10,
d_iname = "ld.so.cache\000\000e\000l\000ournal\000\020SIV\000\210\377\377",
d_count = 0x5,
d_lock = {
{
rlock = {
raw_lock = {
{
head_tail = 0x3232,
tickets = {
head = 0x32,
tail = 0x32
}
}
},
magic = 0xdead4ead,
owner_cpu = 0xffffffff,
owner = 0xffffffffffffffff
}
}
},
d_op = 0xffffffff81618f80,
d_sb = 0xffff88016d411800,
d_time = 0x0,
d_fsdata = 0x0,
d_lru = {
next = 0xffff880056495328,
prev = 0xffff880056495328
},
d_child = {
next = 0xffff88010e91d770,
prev = 0xffff8800584ae408
},
d_subdirs = {
next = 0xffff880056495348,
prev = 0xffff880056495348
},
d_u = {
d_alias = {
next = 0xffff88013d235b58,
prev = 0xffff88013d235b58
},
d_rcu = {
next = 0xffff88013d235b58,
func = 0xffff88013d235b58
}

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