# git rev-parse -q --verify e3a36eb6dfaeea8175c05d5915dcf0b939be6dab^{commit} e3a36eb6dfaeea8175c05d5915dcf0b939be6dab already have revision, skipping fetch # git checkout -q -f -B kisskb e3a36eb6dfaeea8175c05d5915dcf0b939be6dab # git clean -qxdf # < git log -1 # commit e3a36eb6dfaeea8175c05d5915dcf0b939be6dab # Author: Christoph Hellwig # Date: Wed Mar 11 17:07:10 2020 +0100 # # driver code: clarify and fix platform device DMA mask allocation # # This does three inter-related things to clarify the usage of the # platform device dma_mask field. In the process, fix the bug introduced # by cdfee5623290 ("driver core: initialize a default DMA mask for # platform device") that caused Artem Tashkinov's laptop to not boot with # newer Fedora kernels. # # This does: # # - First off, rename the field to "platform_dma_mask" to make it # greppable. # # We have way too many different random fields called "dma_mask" in # various data structures, where some of them are actual masks, and # some of them are just pointers to the mask. And the structures all # have pointers to each other, or embed each other inside themselves, # and "pdev" sometimes means "platform device" and sometimes it means # "PCI device". # # So to make it clear in the code when you actually use this new field, # give it a unique name (it really should be something even more unique # like "platform_device_dma_mask", since it's per platform device, not # per platform, but that gets old really fast, and this is unique # enough in context). # # To further clarify when the field gets used, initialize it when we # actually start using it with the default value. # # - Then, use this field instead of the random one-off allocation in # platform_device_register_full() that is now unnecessary since we now # already have a perfectly fine allocation for it in the platform # device structure. # # - The above then allows us to fix the actual bug, where the error path # of platform_device_register_full() would unconditionally free the # platform device DMA allocation with 'kfree()'. # # That kfree() was dont regardless of whether the allocation had been # done earlier with the (now removed) kmalloc, or whether # setup_pdev_dma_masks() had already been used and the dma_mask pointer # pointed to the mask that was part of the platform device. # # It seems most people never triggered the error path, or only triggered # it from a call chain that set an explicit pdevinfo->dma_mask value (and # thus caused the unnecessary allocation that was "cleaned up" in the # error path) before calling platform_device_register_full(). # # Robin Murphy points out that in Artem's case the wdat_wdt driver failed # in platform_device_add(), and that was the one that had called # platform_device_register_full() with pdevinfo.dma_mask = 0, and would # have caused that kfree() of pdev.dma_mask corrupting the heap. # # A later unrelated kmalloc() then oopsed due to the heap corruption. # # Fixes: cdfee5623290 ("driver core: initialize a default DMA mask for platform device") # Reported-bisected-and-tested-by: Artem S. Tashkinov # Reviewed-by: Robin Murphy # Cc: Greg Kroah-Hartman # Signed-off-by: Christoph Hellwig # Signed-off-by: Linus Torvalds # < /opt/cross/kisskb/korg/gcc-8.1.0-nolibc/m68k-linux/bin/m68k-linux-gcc --version # < /opt/cross/kisskb/korg/gcc-8.1.0-nolibc/m68k-linux/bin/m68k-linux-ld --version # < git log --format=%s --max-count=1 e3a36eb6dfaeea8175c05d5915dcf0b939be6dab # < make -s -j 48 ARCH=m68k O=/kisskb/build/linus_m5272c3_defconfig_m68k-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/m68k-linux/bin/m68k-linux- m5272c3_defconfig # < make -s -j 48 ARCH=m68k O=/kisskb/build/linus_m5272c3_defconfig_m68k-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/m68k-linux/bin/m68k-linux- help # make -s -j 48 ARCH=m68k O=/kisskb/build/linus_m5272c3_defconfig_m68k-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/m68k-linux/bin/m68k-linux- olddefconfig # make -s -j 48 ARCH=m68k O=/kisskb/build/linus_m5272c3_defconfig_m68k-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/m68k-linux/bin/m68k-linux- /kisskb/src/drivers/net/ethernet/freescale/fec_main.c: In function 'fec_restart': /kisskb/src/drivers/net/ethernet/freescale/fec_main.c:915:6: warning: unused variable 'val' [-Wunused-variable] u32 val; ^~~ /kisskb/src/drivers/net/ethernet/freescale/fec_main.c: In function 'fec_get_mac': /kisskb/src/drivers/net/ethernet/freescale/fec_main.c:1643:28: warning: unused variable 'pdata' [-Wunused-variable] struct fec_platform_data *pdata = dev_get_platdata(&fep->pdev->dev); ^~~~~ In file included from /kisskb/src/arch/m68k/include/asm/atomic.h:7, from /kisskb/src/include/linux/atomic.h:7, from /kisskb/src/include/linux/spinlock.h:445, from /kisskb/src/include/linux/seqlock.h:36, from /kisskb/src/include/linux/time.h:6, from /kisskb/src/include/linux/stat.h:19, from /kisskb/src/include/linux/module.h:13, from /kisskb/src/net/core/filter.c:20: /kisskb/src/net/core/filter.c: In function 'bpf_clear_redirect_map': /kisskb/src/arch/m68k/include/asm/cmpxchg.h:137:3: warning: value computed is not used [-Wunused-value] ((__typeof__(*(ptr)))__cmpxchg_local_generic((ptr), (unsigned long)(o),\ ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ (unsigned long)(n), sizeof(*(ptr)))) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ /kisskb/src/include/asm-generic/cmpxchg.h:106:28: note: in expansion of macro 'cmpxchg_local' #define cmpxchg(ptr, o, n) cmpxchg_local((ptr), (o), (n)) ^~~~~~~~~~~~~ /kisskb/src/net/core/filter.c:3516:4: note: in expansion of macro 'cmpxchg' cmpxchg(&ri->map, map, NULL); ^~~~~~~ Completed OK # rm -rf /kisskb/build/linus_m5272c3_defconfig_m68k-gcc8 # Build took: 0:00:26.674995