Fix NPE discovered by running bpf kselftest #4729
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Previously sk_msg_memcopy_from_iter returns the copied bytes from the
last copy_from_iter{,_nocache} call upon success.
This commit changes it to return the total number of copied bytes on
success.
Signed-off-by: Levi Zim <[email protected]>
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. This commit changes it to use the real copied bytes. Signed-off-by: Levi Zim <[email protected]>
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Pull request for series with
subject: Fix NPE discovered by running bpf kselftest
version: 1
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=913470