# git rev-parse -q --verify bddac7c1e02ba47f0570e494c9289acea3062cc1^{commit} bddac7c1e02ba47f0570e494c9289acea3062cc1 already have revision, skipping fetch # git checkout -q -f -B kisskb bddac7c1e02ba47f0570e494c9289acea3062cc1 # git clean -qxdf # < git log -1 # commit bddac7c1e02ba47f0570e494c9289acea3062cc1 # Author: Linus Torvalds # Date: Sat Mar 26 10:42:04 2022 -0700 # # Revert "swiotlb: rework "fix info leak with DMA_FROM_DEVICE"" # # This reverts commit aa6f8dcbab473f3a3c7454b74caa46d36cdc5d13. # # It turns out this breaks at least the ath9k wireless driver, and # possibly others. # # What the ath9k driver does on packet receive is to set up the DMA # transfer with: # # int ath_rx_init(..) # .. # bf->bf_buf_addr = dma_map_single(sc->dev, skb->data, # common->rx_bufsize, # DMA_FROM_DEVICE); # # and then the receive logic (through ath_rx_tasklet()) will fetch # incoming packets # # static bool ath_edma_get_buffers(..) # .. # dma_sync_single_for_cpu(sc->dev, bf->bf_buf_addr, # common->rx_bufsize, DMA_FROM_DEVICE); # # ret = ath9k_hw_process_rxdesc_edma(ah, rs, skb->data); # if (ret == -EINPROGRESS) { # /*let device gain the buffer again*/ # dma_sync_single_for_device(sc->dev, bf->bf_buf_addr, # common->rx_bufsize, DMA_FROM_DEVICE); # return false; # } # # and it's worth noting how that first DMA sync: # # dma_sync_single_for_cpu(..DMA_FROM_DEVICE); # # is there to make sure the CPU can read the DMA buffer (possibly by # copying it from the bounce buffer area, or by doing some cache flush). # The iommu correctly turns that into a "copy from bounce bufer" so that # the driver can look at the state of the packets. # # In the meantime, the device may continue to write to the DMA buffer, but # we at least have a snapshot of the state due to that first DMA sync. # # But that _second_ DMA sync: # # dma_sync_single_for_device(..DMA_FROM_DEVICE); # # is telling the DMA mapping that the CPU wasn't interested in the area # because the packet wasn't there. In the case of a DMA bounce buffer, # that is a no-op. # # Note how it's not a sync for the CPU (the "for_device()" part), and it's # not a sync for data written by the CPU (the "DMA_FROM_DEVICE" part). # # Or rather, it _should_ be a no-op. That's what commit aa6f8dcbab47 # broke: it made the code bounce the buffer unconditionally, and changed # the DMA_FROM_DEVICE to just unconditionally and illogically be # DMA_TO_DEVICE. # # [ Side note: purely within the confines of the swiotlb driver it wasn't # entirely illogical: The reason it did that odd DMA_FROM_DEVICE -> # DMA_TO_DEVICE conversion thing is because inside the swiotlb driver, # it uses just a swiotlb_bounce() helper that doesn't care about the # whole distinction of who the sync is for - only which direction to # bounce. # # So it took the "sync for device" to mean that the CPU must have been # the one writing, and thought it meant DMA_TO_DEVICE. ] # # Also note how the commentary in that commit was wrong, probably due to # that whole confusion, claiming that the commit makes the swiotlb code # # "bounce unconditionally (that is, also # when dir == DMA_TO_DEVICE) in order do avoid synchronising back stale # data from the swiotlb buffer" # # which is nonsensical for two reasons: # # - that "also when dir == DMA_TO_DEVICE" is nonsensical, as that was # exactly when it always did - and should do - the bounce. # # - since this is a sync for the device (not for the CPU), we're clearly # fundamentally not coping back stale data from the bounce buffers at # all, because we'd be copying *to* the bounce buffers. # # So that commit was just very confused. It confused the direction of the # synchronization (to the device, not the cpu) with the direction of the # DMA (from the device). # # Reported-and-bisected-by: Oleksandr Natalenko # Reported-by: Olha Cherevyk # Cc: Halil Pasic # Cc: Christoph Hellwig # Cc: Kalle Valo # Cc: Robin Murphy # Cc: Toke Høiland-Jørgensen # Cc: Maxime Bizon # Cc: Johannes Berg # Signed-off-by: Linus Torvalds # < /opt/cross/kisskb/fe-x86-64-core-i7-2017.05/bin/x86_64-linux-gcc --version # < /opt/cross/kisskb/fe-x86-64-core-i7-2017.05/bin/x86_64-linux-ld --version # < git log --format=%s --max-count=1 bddac7c1e02ba47f0570e494c9289acea3062cc1 # < make -s -j 32 ARCH=um O=/kisskb/build/linus_um-allmodconfig_um-x86_64 CROSS_COMPILE=/opt/cross/kisskb/fe-x86-64-core-i7-2017.05/bin/x86_64-linux- SUBARCH=x86_64 allmodconfig # Added to kconfig CONFIG_STANDALONE=y # Added to kconfig CONFIG_KCOV=n # Added to kconfig CONFIG_GCC_PLUGINS=n # Added to kconfig CONFIG_GCC_PLUGIN_CYC_COMPLEXITY=n # Added to kconfig CONFIG_GCC_PLUGIN_SANCOV=n # Added to kconfig CONFIG_GCC_PLUGIN_LATENT_ENTROPY=n # Added to kconfig CONFIG_GCC_PLUGIN_STRUCTLEAK=n # Added to kconfig CONFIG_GCC_PLUGIN_RANDSTRUCT=n # Added to kconfig CONFIG_UML_NET=n # Added to kconfig CONFIG_UML_NET_ETHERTAP=n # Added to kconfig CONFIG_UML_NET_TUNTAP=n # Added to kconfig CONFIG_UML_NET_SLIP=n # Added to kconfig CONFIG_UML_NET_DAEMON=n # Added to kconfig CONFIG_UML_NET_VDE=n # Added to kconfig CONFIG_UML_NET_MCAST=n # Added to kconfig CONFIG_UML_NET_PCAP=n # Added to kconfig CONFIG_UML_NET_SLIRP=n # Added to kconfig CONFIG_GCOV_KERNEL=n # Added to kconfig CONFIG_DEBUG_INFO_BTF=n # Added to kconfig CONFIG_BPF_PRELOAD=n # < make -s -j 32 ARCH=um O=/kisskb/build/linus_um-allmodconfig_um-x86_64 CROSS_COMPILE=/opt/cross/kisskb/fe-x86-64-core-i7-2017.05/bin/x86_64-linux- SUBARCH=x86_64 help # make -s -j 32 ARCH=um O=/kisskb/build/linus_um-allmodconfig_um-x86_64 CROSS_COMPILE=/opt/cross/kisskb/fe-x86-64-core-i7-2017.05/bin/x86_64-linux- SUBARCH=x86_64 olddefconfig .config:12165:warning: override: reassigning to symbol GCC_PLUGIN_SANCOV .config:12168:warning: override: reassigning to symbol GCC_PLUGIN_RANDSTRUCT .config:12170:warning: override: reassigning to symbol UML_NET_ETHERTAP .config:12172:warning: override: reassigning to symbol UML_NET_SLIP .config:12175:warning: override: reassigning to symbol UML_NET_MCAST .config:12177:warning: override: reassigning to symbol UML_NET_SLIRP # make -s -j 32 ARCH=um O=/kisskb/build/linus_um-allmodconfig_um-x86_64 CROSS_COMPILE=/opt/cross/kisskb/fe-x86-64-core-i7-2017.05/bin/x86_64-linux- SUBARCH=x86_64 In file included from /kisskb/src/arch/x86/um/asm/processor.h:41:0, from /kisskb/src/include/linux/mutex.h:19, from /kisskb/src/include/linux/kernfs.h:11, from /kisskb/src/include/linux/sysfs.h:16, from /kisskb/src/include/linux/kobject.h:20, from /kisskb/src/include/linux/pci.h:35, from /kisskb/src/drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_topology.c:26: /kisskb/src/drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_topology.c: In function 'kfd_cpumask_to_apic_id': /kisskb/src/arch/um/include/asm/processor-generic.h:103:18: error: called object is not a function or function pointer #define cpu_data (&boot_cpu_data) ^ /kisskb/src/drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_topology.c:1557:9: note: in expansion of macro 'cpu_data' return cpu_data(first_cpu_of_numa_node).apicid; ^ /kisskb/src/drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_topology.c:1561:1: error: control reaches end of non-void function [-Werror=return-type] } ^ cc1: all warnings being treated as errors make[5]: *** [/kisskb/src/scripts/Makefile.build:288: drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_topology.o] Error 1 make[5]: *** Waiting for unfinished jobs.... make[4]: *** [/kisskb/src/scripts/Makefile.build:550: drivers/gpu/drm/amd/amdgpu] Error 2 make[4]: *** Waiting for unfinished jobs.... /kisskb/src/drivers/infiniband/sw/rdmavt/qp.c: In function 'rvt_wss_llc_size': /kisskb/src/drivers/infiniband/sw/rdmavt/qp.c:88:22: error: 'struct cpuinfo_um' has no member named 'x86_cache_size' return boot_cpu_data.x86_cache_size; ^ /kisskb/src/drivers/infiniband/sw/rdmavt/qp.c: In function 'cacheless_memcpy': /kisskb/src/drivers/infiniband/sw/rdmavt/qp.c:100:2: error: implicit declaration of function '__copy_user_nocache' [-Werror=implicit-function-declaration] __copy_user_nocache(dst, (void __user *)src, n, 0); ^ /kisskb/src/drivers/infiniband/sw/rdmavt/qp.c: In function 'rvt_wss_llc_size': /kisskb/src/drivers/infiniband/sw/rdmavt/qp.c:89:1: error: control reaches end of non-void function [-Werror=return-type] } ^ cc1: all warnings being treated as errors make[5]: *** [/kisskb/src/scripts/Makefile.build:288: drivers/infiniband/sw/rdmavt/qp.o] Error 1 make[5]: *** Waiting for unfinished jobs.... make[4]: *** [/kisskb/src/scripts/Makefile.build:550: drivers/infiniband/sw/rdmavt] Error 2 make[4]: *** Waiting for unfinished jobs.... make[3]: *** [/kisskb/src/scripts/Makefile.build:550: drivers/gpu/drm] Error 2 make[2]: *** [/kisskb/src/scripts/Makefile.build:550: drivers/gpu] Error 2 make[2]: *** Waiting for unfinished jobs.... make[3]: *** [/kisskb/src/scripts/Makefile.build:550: drivers/infiniband/sw] Error 2 make[3]: *** Waiting for unfinished jobs.... /kisskb/src/drivers/infiniband/hw/qib/qib_wc_x86_64.c: In function 'qib_unordered_wc': /kisskb/src/drivers/infiniband/hw/qib/qib_wc_x86_64.c:149:22: error: 'struct cpuinfo_um' has no member named 'x86_vendor' return boot_cpu_data.x86_vendor != X86_VENDOR_AMD; ^ /kisskb/src/drivers/infiniband/hw/qib/qib_wc_x86_64.c:149:37: error: 'X86_VENDOR_AMD' undeclared (first use in this function) return boot_cpu_data.x86_vendor != X86_VENDOR_AMD; ^ /kisskb/src/drivers/infiniband/hw/qib/qib_wc_x86_64.c:149:37: note: each undeclared identifier is reported only once for each function it appears in /kisskb/src/drivers/infiniband/hw/qib/qib_wc_x86_64.c:150:1: error: control reaches end of non-void function [-Werror=return-type] } ^ cc1: all warnings being treated as errors make[5]: *** [/kisskb/src/scripts/Makefile.build:288: drivers/infiniband/hw/qib/qib_wc_x86_64.o] Error 1 make[5]: *** Waiting for unfinished jobs.... make[4]: *** [/kisskb/src/scripts/Makefile.build:550: drivers/infiniband/hw/qib] Error 2 make[4]: *** Waiting for unfinished jobs.... make[3]: *** [/kisskb/src/scripts/Makefile.build:550: drivers/infiniband/hw] Error 2 make[2]: *** [/kisskb/src/scripts/Makefile.build:550: drivers/infiniband] Error 2 make[1]: *** [/kisskb/src/Makefile:1832: drivers] Error 2 make: *** [Makefile:219: __sub-make] Error 2 Command 'make -s -j 32 ARCH=um O=/kisskb/build/linus_um-allmodconfig_um-x86_64 CROSS_COMPILE=/opt/cross/kisskb/fe-x86-64-core-i7-2017.05/bin/x86_64-linux- SUBARCH=x86_64 ' returned non-zero exit status 2 # rm -rf /kisskb/build/linus_um-allmodconfig_um-x86_64 # Build took: 0:09:33.250575