On 2024-11-30 21:38, Levi Zim via B4 Relay wrote:
I found that bpf kselftest sockhash::test_txmsg_cork_hangs in
test_sockmap.c triggers a kernel NULL pointer dereference:
BUG: kernel NULL pointer dereference, address: 0000000000000008
? __die_body+0x6e/0xb0
? __die+0x8b/0xa0
? page_fault_oops+0x358/0x3c0
? local_clock+0x19/0x30
? lock_release+0x11b/0x440
? kernelmode_fixup_or_oops+0x54/0x60
? __bad_area_nosemaphore+0x4f/0x210
? mmap_read_unlock+0x13/0x30
? bad_area_nosemaphore+0x16/0x20
? do_user_addr_fault+0x6fd/0x740
? prb_read_valid+0x1d/0x30
? exc_page_fault+0x55/0xd0
? asm_exc_page_fault+0x2b/0x30
? splice_to_socket+0x52e/0x630
? shmem_file_splice_read+0x2b1/0x310
direct_splice_actor+0x47/0x70
splice_direct_to_actor+0x133/0x300
? do_splice_direct+0x90/0x90
do_splice_direct+0x64/0x90
? __ia32_sys_tee+0x30/0x30
do_sendfile+0x214/0x300
__se_sys_sendfile64+0x8e/0xb0
__x64_sys_sendfile64+0x25/0x30
x64_sys_call+0xb82/0x2840
do_syscall_64+0x75/0x110
entry_SYSCALL_64_after_hwframe+0x4b/0x53
This is caused by tcp_bpf_sendmsg() returning a larger value(12289) than
size(8192), which causes the while loop in splice_to_socket() to release
an uninitialized pipe buf.
The underlying cause is that this code assumes sk_msg_memcopy_from_iter()
will copy all bytes upon success but it actually might only copy part of
it.
I am not sure what Fixes tag I should put. Git blame leads me to a
refactor commit
and I am not familiar with this part of code base. Any suggestions?
This series change sk_msg_memcopy_from_iter() to return copied bytes on
success and tcp_bpf_sendmsg() to use the real copied bytes instead of
assuming all bytes gets copied.
Signed-off-by: Levi Zim <rsworktech@xxxxxxxxxxx>
---
Levi Zim (2):
skmsg: return copied bytes in sk_msg_memcopy_from_iter
tcp_bpf: fix copied value in tcp_bpf_sendmsg
net/core/skmsg.c | 5 +++--
net/ipv4/tcp_bpf.c | 8 ++++----
2 files changed, 7 insertions(+), 6 deletions(-)
---
base-commit: f1cd565ce57760923d5e0fbd9e9914b415c0620a
change-id: 20241130-tcp-bpf-sendmsg-ff3c9d84e693
Best regards,
