Memory modified after free: Most recently used by acpitask

Hi,

Just got a panic on a 6-CURRENT (Thu Nov 18 16:36:35 GMT 2004) machine,
while copying a large amount of data around.

Seems to be an ACPI related reuse-after-free.  As far as I can tell, 20
bytes into the acpi_task structure is (int)ta_flags within the embedded
struct task, but I can't see use of this field in the ACPI code so ACPI
may be a red herring.

Sadly, I don't have a core dump as the machine double faulted during the
attempt.

Gavin


# cp -Rp /usr/* /var/usr
[about 10 minutes later]
Memory modified after free 0xc44a8420(28) val=0 _at_ 0xc44a8434
panic: Most recently used by acpitask

cpuid = 1
KDB: enter: panic
[thread 100103]
Stopped at      kdb_enter+0x2c: leave
db> tr
kdb_enter(c081145f,100,c3929480,1c,c44a843c) at kdb_enter+0x2c
panic(c082b121,c0a312d0,c082b0f2,c44a8420,1c) at panic+0x17f
mtrash_ctor(c44a8420,20,0,502) at mtrash_ctor+0x5f
uma_zalloc_arg(c1052420,0,502) at uma_zalloc_arg+0x3d8
malloc(20,c08a80c0,502,0,0) at malloc+0x6b
softdep_setup_directory_add(d7583cb0,c5379348,28,0,f769f) at
softdep_setup_directory_add+0x61
ufs_direnter(c5e9dac8,c58aa78c,ecc95924,ecc95c0c,0,c53e4834,ecc95c0c,ecc95924) at ufs_direnter+0x6ff
ufs_makeinode(ecc95bf8,ecc95c0c,ecc95a6c,ecc95b2c,c0668f16) at
ufs_makeinode+0x267
ufs_create(ecc95a70) at ufs_create+0x25
vn_open_cred(ecc95be4,ecc95ce4,16d,c3480780,4) at vn_open_cred+0x49a
vn_open(ecc95be4,ecc95ce4,16d,4,c08d2040,8,c081a444,3bc) at vn_open+0x1e
kern_open(c3929480,804b868,0,602,816d) at kern_open+0xd6
open(c3929480,ecc95d14,3,1015d,286) at open+0x18
syscall(804002f,2f,bfbf002f,804b89d,1) at syscall+0x128
Xint0x80_syscall() at Xint0x80_syscall+0x1f
--- syscall (5, FreeBSD ELF32, open), eip = 0x280c1bdf, esp =
0xbfbfeb3c, ebp = 0xbfbfeb88 ---


Gavin