Re: [syzbot] [mm?] [f2fs?] [exfat?] memory leak in __kfree_rcu_sheaf

syzbot
2026-03-10T06:29:06Z

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
memory leak in copy_process

BUG: memory leak
unreferenced object 0xffff888101799d80 (size 184):
comm "kthreadd", pid 2, jiffies 4294948049
hex dump (first 32 bytes):
01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0a 21 00 00 00 00 00 00 58 78 fd 01 81 88 ff ff .!......Xx......
backtrace (crc e9f8bd9):
kmemleak_alloc_recursive include/linux/kmemleak.h:45 [inline]
slab_post_alloc_hook mm/slub.c:4552 [inline]
slab_alloc_node mm/slub.c:4874 [inline]
kmem_cache_alloc_noprof+0x372/0x480 mm/slub.c:4881
alloc_pid+0xe4/0x850 kernel/pid.c:189
copy_process+0x1a97/0x28c0 kernel/fork.c:2239
kernel_clone+0xac/0x6e0 kernel/fork.c:2654
kernel_thread+0x80/0xb0 kernel/fork.c:2715
create_kthread kernel/kthread.c:459 [inline]
kthreadd+0x186/0x250 kernel/kthread.c:817
ret_from_fork+0x23c/0x4b0 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

BUG: memory leak
unreferenced object 0xffff88810b0d7b40 (size 184):
comm "kthreadd", pid 2, jiffies 4294948049
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace (crc ddb1bc35):
kmemleak_alloc_recursive include/linux/kmemleak.h:45 [inline]
slab_post_alloc_hook mm/slub.c:4552 [inline]
slab_alloc_node mm/slub.c:4874 [inline]
kmem_cache_alloc_noprof+0x372/0x480 mm/slub.c:4881
prepare_creds+0x22/0x600 kernel/cred.c:185
copy_creds+0x44/0x290 kernel/cred.c:286
copy_process+0x7a7/0x28c0 kernel/fork.c:2084
kernel_clone+0xac/0x6e0 kernel/fork.c:2654
kernel_thread+0x80/0xb0 kernel/fork.c:2715
create_kthread kernel/kthread.c:459 [inline]
kthreadd+0x186/0x250 kernel/kthread.c:817
ret_from_fork+0x23c/0x4b0 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

BUG: memory leak
unreferenced object 0xffff88810b91e4a0 (size 32):
comm "kthreadd", pid 2, jiffies 4294948049
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
f8 6e 0a 00 81 88 ff ff 00 00 00 00 00 00 00 00 .n..............
backtrace (crc 13ba6aa5):
kmemleak_alloc_recursive include/linux/kmemleak.h:45 [inline]
slab_post_alloc_hook mm/slub.c:4552 [inline]
slab_alloc_node mm/slub.c:4874 [inline]
__do_kmalloc_node mm/slub.c:5267 [inline]
__kmalloc_noprof+0x3bd/0x560 mm/slub.c:5280
kmalloc_noprof include/linux/slab.h:954 [inline]
kzalloc_noprof include/linux/slab.h:1188 [inline]
lsm_blob_alloc+0x4d/0x80 security/security.c:192
lsm_cred_alloc security/security.c:209 [inline]
security_prepare_creds+0x2d/0x290 security/security.c:2763
prepare_creds+0x395/0x600 kernel/cred.c:215
copy_creds+0x44/0x290 kernel/cred.c:286
copy_process+0x7a7/0x28c0 kernel/fork.c:2084
kernel_clone+0xac/0x6e0 kernel/fork.c:2654
kernel_thread+0x80/0xb0 kernel/fork.c:2715
create_kthread kernel/kthread.c:459 [inline]
kthreadd+0x186/0x250 kernel/kthread.c:817
ret_from_fork+0x23c/0x4b0 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

connection error: failed to recv *flatrpc.ExecutorMessageRawT: EOF

Tested on:

commit: 1f318b96 Linux 7.0-rc3
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1224694a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=2c6ad6fefffa76b1
dashboard link: https://syzkaller.appspot.com/bug?extid=cae7809e9dc1459e4e63
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
patch: https://syzkaller.appspot.com/x/patch.diff?x=110faf5a580000