kernel/linux.git/net/smc/smc_loopback.c, branch v6.12.80

net/smc: fix warning in smc_rx_splice() when calling get_page()

2025-10-02T11:44:10+00:00

[ Upstream commit a35c04de2565db191726b5741e6b66a35002c652 ] smc_lo_register_dmb() allocates DMB buffers with kzalloc(), which are later passed to get_page() in smc_rx_splice(). Since kmalloc memory is not page-backed, this triggers WARN_ON_ONCE() in get_page() and prevents holding a refcount on the buffer. This can lead to use-after-free if the memory is released before splice_to_pipe() completes. Use folio_alloc() instead, ensuring DMBs are page-backed and safe for get_page(). WARNING: CPU: 18 PID: 12152 at ./include/linux/mm.h:1330 smc_rx_splice+0xaf8/0xe20 [smc] CPU: 18 UID: 0 PID: 12152 Comm: smcapp Kdump: loaded Not tainted 6.17.0-rc3-11705-g9cf4672ecfee #10 NONE Hardware name: IBM 3931 A01 704 (z/VM 7.4.0) Krnl PSW : 0704e00180000000 000793161032696c (smc_rx_splice+0xafc/0xe20 [smc]) R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:2 PM:0 RI:0 EA:3 Krnl GPRS: 0000000000000000 001cee80007d3001 00077400000000f8 0000000000000005 0000000000000001 001cee80007d3006 0007740000001000 001c000000000000 000000009b0c99e0 0000000000001000 001c0000000000f8 001c000000000000 000003ffcc6f7c88 0007740003e98000 0007931600000005 000792969b2ff7b8 Krnl Code: 0007931610326960: af000000 mc 0,0 0007931610326964: a7f4ff43 brc 15,00079316103267ea #0007931610326968: af000000 mc 0,0 >000793161032696c: a7f4ff3f brc 15,00079316103267ea 0007931610326970: e320f1000004 lg %r2,256(%r15) 0007931610326976: c0e53fd1b5f5 brasl %r14,000793168fd5d560 000793161032697c: a7f4fbb5 brc 15,00079316103260e6 0007931610326980: b904002b lgr %r2,%r11 Call Trace: smc_rx_splice+0xafc/0xe20 [smc] smc_rx_splice+0x756/0xe20 [smc]) smc_rx_recvmsg+0xa74/0xe00 [smc] smc_splice_read+0x1ce/0x3b0 [smc] sock_splice_read+0xa2/0xf0 do_splice_read+0x198/0x240 splice_file_to_pipe+0x7e/0x110 do_splice+0x59e/0xde0 __do_splice+0x11a/0x2d0 __s390x_sys_splice+0x140/0x1f0 __do_syscall+0x122/0x280 system_call+0x6e/0x90 Last Breaking-Event-Address: smc_rx_splice+0x960/0xe20 [smc] ---[ end trace 0000000000000000 ]--- Fixes: f7a22071dbf3 ("net/smc: implement DMB-related operations of loopback-ism") Reviewed-by: Mahanta Jambigi Signed-off-by: Sidraya Jayagond Link: https://patch.msgid.link/20250917184220.801066-1-sidraya@linux.ibm.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

net/smc: implement DMB-merged operations of loopback-ism

2024-04-30T11:24:49+00:00

This implements operations related to merging sndbuf with peer DMB in loopback-ism. The DMB won't be freed until no sndbuf is attached to it. Signed-off-by: Wen Gu Reviewed-by: Wenjia Zhang Reviewed-and-tested-by: Jan Karcher Signed-off-by: Paolo Abeni

net/smc: register loopback-ism into SMC-D device list

2024-04-30T11:24:48+00:00

After the loopback-ism device is ready, add it to the SMC-D device list as an ISMv2 device, and always keep it at the beginning to ensure it is preferred for providing a shortcut for data transfer within the same kernel. Signed-off-by: Wen Gu Reviewed-by: Wenjia Zhang Reviewed-and-tested-by: Jan Karcher Signed-off-by: Paolo Abeni

net/smc: implement DMB-related operations of loopback-ism

2024-04-30T11:24:48+00:00

This implements DMB (un)registration and data move operations of loopback-ism device. Signed-off-by: Wen Gu Reviewed-by: Wenjia Zhang Reviewed-and-tested-by: Jan Karcher Signed-off-by: Paolo Abeni

net/smc: implement ID-related operations of loopback-ism

2024-04-30T11:24:48+00:00

This implements operations related to IDs for the loopback-ism device. loopback-ism uses an Extended GID that is a 128-bit GID instead of the existing ISM 64-bit GID, and uses the CHID defined with the reserved value 0xFFFF. Signed-off-by: Wen Gu Reviewed-by: Wenjia Zhang Reviewed-and-tested-by: Jan Karcher Signed-off-by: Paolo Abeni

net/smc: introduce loopback-ism for SMC intra-OS shortcut

2024-04-30T11:24:48+00:00

This introduces a kind of Emulated-ISM device named loopback-ism for SMCv2.1. The loopback-ism device is currently exclusive for SMC usage, and aims to provide an SMC shortcut for sockets within the same kernel, leading to improved intra-OS traffic performance. Configuration of this feature is managed through the config SMC_LO. Signed-off-by: Wen Gu Reviewed-by: Gerd Bayer Reviewed-by: Wenjia Zhang Reviewed-and-tested-by: Jan Karcher Signed-off-by: Paolo Abeni