On 1/9/2019 5:01 PM, Catalin Marinas wrote:
Hi Prateek,
On Wed, Jan 09, 2019 at 02:09:22PM +0530, Prateek Patel wrote:
From: Sri Krishna chowdary <schowdary@xxxxxxxxxx>
kmemleak detects allocated objects as leaks if not accessed for
default scan time. The memory allocated using avc_alloc_node
is freed using rcu mechanism when nodes are reclaimed or on
avc_flush. So, there is no real leak here and kmemleak_scan
detects it as a leak which is false positive. Hence, mark it as
kmemleak_not_leak.
In theory, kmemleak should detect the node->rhead in the lists used by
call_rcu() and not report it as a leak. Which RCU options do you have
enabled (just to check whether kmemleak tracks the RCU internal lists)?
Also, does this leak eventually disappear without your patch? Does
echo dump=0xffffffc0dd1a0e60 > /sys/kernel/debug/kmemleak
still display this object?
Thanks.
Hi Catalin,
It was intermittently showing leak and didn't repro on multiple runs. To
repo, I decreased the
minimum object age for reporting, I found triggering the second scan
just after first is not showing
any leak. Also, without my patch, on echo dump, obj is not displaying.
Is increasing minimum object age for reporting a good idea to handle
such type of issues to
avoid false-positives?
Following is the log:
t186_int:/ # echo scan > /sys/kernel/debug/kmemleak
t186_int:/ # cat /sys/kernel/debug/kmemleak
unreferenced object 0xffffffc1e06424c8 (size 72):
comm "netd", pid 4891, jiffies 4294906431 (age 23.120s)
hex dump (first 32 bytes):
97 01 00 00 1b 00 00 00 0b 00 00 00 57 06 04 00 ............W...
00 00 00 00 ff ff ff ff 01 00 00 00 00 00 00 00 ................
backtrace:
[<ffffff8008275214>] kmem_cache_alloc+0x1ac/0x2c0
[<ffffff80084dcf90>] avc_alloc_node+0x28/0x240
[<ffffff80084dd404>] avc_compute_av+0xa4/0x1d0
[<ffffff80084de1b8>] avc_has_perm+0xf8/0x1b8
[<ffffff80084e37f8>] file_has_perm+0xb8/0xe8
[<ffffff80084e3d64>] match_file+0x44/0x98
[<ffffff80082cc9d4>] iterate_fd+0x84/0xd0
[<ffffff80084e2b3c>] selinux_bprm_committing_creds+0xec/0x230
[<ffffff80084d842c>] security_bprm_committing_creds+0x44/0x60
[<ffffff80082ad020>] install_exec_creds+0x20/0x70
[<ffffff800831b9a4>] load_elf_binary+0x31c/0xd10
[<ffffff80082ae530>] search_binary_handler+0x98/0x288
[<ffffff80082af078>] do_execveat_common.isra.14+0x550/0x6d0
[<ffffff80082af4ac>] SyS_execve+0x4c/0x60
[<ffffff80080839c0>] el0_svc_naked+0x34/0x38
[<ffffffffffffffff>] 0xffffffffffffffff
unreferenced object 0xffffffc1ab3c61b0 (size 72):
comm "crash_dump64", pid 5058, jiffies 4294907834 (age 17.508s)
hex dump (first 32 bytes):
2f 02 00 00 6b 00 00 00 07 00 00 00 53 04 04 00 /...k.......S...
00 00 00 00 ff ff fd ff 01 00 00 00 00 00 00 00 ................
backtrace:
[<ffffff8008275214>] kmem_cache_alloc+0x1ac/0x2c0
[<ffffff80084dcf90>] avc_alloc_node+0x28/0x240
[<ffffff80084dd404>] avc_compute_av+0xa4/0x1d0
[<ffffff80084de084>] avc_has_perm_noaudit+0xe4/0x120
[<ffffff80084e1264>] selinux_inode_permission+0xc4/0x1c8
[<ffffff80084d8fe8>] security_inode_permission+0x60/0x88
[<ffffff80082b2cf4>] __inode_permission2+0x54/0x120
[<ffffff80082b2e30>] inode_permission2+0x38/0x80
[<ffffff80082b4b58>] may_open+0x70/0x128
[<ffffff80082b6fd4>] do_last+0x234/0xee8
[<ffffff80082b7d30>] path_openat+0xa8/0x310
[<ffffff80082b9390>] do_filp_open+0x88/0x108
[<ffffff80082a1fec>] do_sys_open+0x1a4/0x290
[<ffffff80082a215c>] SyS_openat+0x3c/0x50
[<ffffff80080839c0>] el0_svc_naked+0x34/0x38
[<ffffffffffffffff>] 0xffffffffffffffff
unreferenced object 0xffffffc1d3bcf678 (size 72):
comm "mediaserver", pid 5156, jiffies 4294909577 (age 10.536s)
hex dump (first 32 bytes):
0b 02 00 00 e2 01 00 00 07 00 00 00 53 04 04 00 ............S...
00 00 00 00 f7 ff ff ff 01 00 00 00 00 00 00 00 ................
backtrace:
[<ffffff8008275214>] kmem_cache_alloc+0x1ac/0x2c0
[<ffffff80084dcf90>] avc_alloc_node+0x28/0x240
[<ffffff80084dd404>] avc_compute_av+0xa4/0x1d0
[<ffffff80084de084>] avc_has_perm_noaudit+0xe4/0x120
[<ffffff80084e1264>] selinux_inode_permission+0xc4/0x1c8
[<ffffff80084d8fe8>] security_inode_permission+0x60/0x88
[<ffffff80082b2cf4>] __inode_permission2+0x54/0x120
[<ffffff80082b2e30>] inode_permission2+0x38/0x80
[<ffffff80082b4b58>] may_open+0x70/0x128
[<ffffff80082b6fd4>] do_last+0x234/0xee8
[<ffffff80082b7d30>] path_openat+0xa8/0x310
[<ffffff80082b9390>] do_filp_open+0x88/0x108
[<ffffff80082a1fec>] do_sys_open+0x1a4/0x290
[<ffffff80082a21f4>] compat_SyS_openat+0x3c/0x50
[<ffffff80080839c0>] el0_svc_naked+0x34/0x38
[<ffffffffffffffff>] 0xffffffffffffffff
t186_int:/ # echo dump=0xffffffc1d3bcf678 > /sys/kernel/debug/kmemleak
kmemleak: Unknown object at 0xffffffc1d3bcf678
Thanks,
