# git rev-parse -q --verify a58007621be33e9f7c7bed5d5ff8ecb914e1044a^{commit} a58007621be33e9f7c7bed5d5ff8ecb914e1044a already have revision, skipping fetch # git checkout -q -f -B kisskb a58007621be33e9f7c7bed5d5ff8ecb914e1044a # git clean -qxdf # < git log -1 # commit a58007621be33e9f7c7bed5d5ff8ecb914e1044a # Author: Michael Ellerman # Date: Thu Feb 14 15:00:36 2019 +1100 # # powerpc/64s: Fix possible corruption on big endian due to pgd/pud_present() # # In v4.20 we changed our pgd/pud_present() to check for _PAGE_PRESENT # rather than just checking that the value is non-zero, e.g.: # # static inline int pgd_present(pgd_t pgd) # { # - return !pgd_none(pgd); # + return (pgd_raw(pgd) & cpu_to_be64(_PAGE_PRESENT)); # } # # Unfortunately this is broken on big endian, as the result of the # bitwise & is truncated to int, which is always zero because # _PAGE_PRESENT is 0x8000000000000000ul. This means pgd_present() and # pud_present() are always false at compile time, and the compiler # elides the subsequent code. # # Remarkably with that bug present we are still able to boot and run # with few noticeable effects. However under some work loads we are able # to trigger a warning in the ext4 code: # # WARNING: CPU: 11 PID: 29593 at fs/ext4/inode.c:3927 .ext4_set_page_dirty+0x70/0xb0 # CPU: 11 PID: 29593 Comm: debugedit Not tainted 4.20.0-rc1 #1 # ... # NIP .ext4_set_page_dirty+0x70/0xb0 # LR .set_page_dirty+0xa0/0x150 # Call Trace: # .set_page_dirty+0xa0/0x150 # .unmap_page_range+0xbf0/0xe10 # .unmap_vmas+0x84/0x130 # .unmap_region+0xe8/0x190 # .__do_munmap+0x2f0/0x510 # .__vm_munmap+0x80/0x110 # .__se_sys_munmap+0x14/0x30 # system_call+0x5c/0x70 # # The fix is simple, we need to convert the result of the bitwise & to # an int before returning it. # # Thanks to Erhard, Jan Kara and Aneesh for help with debugging. # # Fixes: da7ad366b497 ("powerpc/mm/book3s: Update pmd_present to look at _PAGE_PRESENT bit") # Cc: stable@vger.kernel.org # v4.20+ # Reported-by: Erhard F. # Reviewed-by: Aneesh Kumar K.V # Signed-off-by: Michael Ellerman # < /opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux-gcc --version # < /opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux-ld --version # < git log --format=%s --max-count=1 a58007621be33e9f7c7bed5d5ff8ecb914e1044a # < make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-fixes_ppc40x_defconfig_powerpc-gcc4.6 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux- ppc40x_defconfig # make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-fixes_ppc40x_defconfig_powerpc-gcc4.6 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux- /kisskb/src/kernel/printk/printk.c: In function 'devkmsg_sysctl_set_loglvl': /kisskb/src/kernel/printk/printk.c:186:16: warning: 'old' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/fs/proc/inode.c: In function 'proc_reg_open': /kisskb/src/include/linux/list.h:65:12: warning: 'pdeo' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/fs/proc/inode.c:339:21: note: 'pdeo' was declared here /kisskb/src/drivers/tty/serial/8250/8250_core.c: In function 'univ8250_release_irq': /kisskb/src/drivers/tty/serial/8250/8250_core.c:247:18: warning: 'i' may be used uninitialized in this function [-Wuninitialized] /kisskb/src/drivers/tty/serial/8250/8250_core.c:227:19: note: 'i' was declared here /kisskb/src/drivers/i2c/i2c-core-base.c: In function 'i2c_generic_scl_recovery': /kisskb/src/drivers/i2c/i2c-core-base.c:235:5: warning: 'ret' may be used uninitialized in this function [-Wuninitialized] INFO: Uncompressed kernel (size 0x5415a0) overlaps the address of the wrapper(0x400000) INFO: Fixing the link_address of wrapper to (0x600000) INFO: Uncompressed kernel (size 0x5415a0) overlaps the address of the wrapper(0x400000) INFO: Fixing the link_address of wrapper to (0x600000) INFO: Uncompressed kernel (size 0x530f2c) overlaps the address of the wrapper(0x400000) INFO: Fixing the link_address of wrapper to (0x600000) INFO: Uncompressed kernel (size 0x5415a0) overlaps the address of the wrapper(0x400000) INFO: Fixing the link_address of wrapper to (0x600000) INFO: Uncompressed kernel (size 0x5415a0) overlaps the address of the wrapper(0x400000) INFO: Fixing the link_address of wrapper to (0x600000) Image Name: Linux-5.0.0-rc1-ga58007621be3 Created: Sun Feb 17 20:17:06 2019 Image Type: PowerPC Linux Kernel Image (gzip compressed) Data Size: 2639363 Bytes = 2577.50 KiB = 2.52 MiB Load Address: 00000000 Entry Point: 00000000 Image Name: Linux-5.0.0-rc1-ga58007621be3 Created: Sun Feb 17 20:17:07 2019 Image Type: PowerPC Linux Kernel Image (gzip compressed) Data Size: 2671048 Bytes = 2608.45 KiB = 2.55 MiB Load Address: 00600000 Entry Point: 00601758 Image Name: Linux-5.0.0-rc1-ga58007621be3 Created: Sun Feb 17 20:17:07 2019 Image Type: PowerPC Linux Kernel Image (gzip compressed) Data Size: 2671440 Bytes = 2608.83 KiB = 2.55 MiB Load Address: 00600000 Entry Point: 006019cc Completed OK # rm -rf /kisskb/build/powerpc-fixes_ppc40x_defconfig_powerpc-gcc4.6 # Build took: 0:00:37.725770