On Wed, Sep 07, 2016 at 10:28:56PM +0800, kbuild test robot wrote: > Hi Kirill, > > [auto build test ERROR on linus/master] > [also build test ERROR on v4.8-rc5 next-20160907] > [if your patch is applied to the wrong git tree, please drop us a note to help improve the system] > [Suggest to use git(>=2.9.0) format-patch --base=<commit> (or --base=auto for convenience) to record what (public, well-known) commit your patch series was built on] > [Check https://git-scm.com/docs/git-format-patch for more information] > > url: https://github.com/0day-ci/linux/commits/Kirill-A-Shutemov/ipc-shm-fix-crash-if-CONFIG_SHMEM-is-not-set/20160907-204216 > config: sh-rsk7201_defconfig (attached as .config) > compiler: sh4-linux-gnu-gcc (Debian 5.4.0-6) 5.4.0 20160609 > reproduce: > wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross > chmod +x ~/bin/make.cross > # save the attached .config to linux build tree > make.cross ARCH=sh > > All errors (new ones prefixed by >>): > > ipc/shm.c: In function 'shm_get_unmapped_area': > >> ipc/shm.c:477:25: error: 'struct mm_struct' has no member named 'get_unmapped_area' > get_area = current->mm->get_unmapped_area; Urghh... no-MMU.. This should work for them too. >From ad99dd548250fede88737ac0b0009e9a0e283b07 Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> Date: Wed, 7 Sep 2016 13:57:20 +0300 Subject: [PATCH] ipc/shm: fix crash if CONFIG_SHMEM is not set Commit c01d5b300774 makes use of shm_get_unmapped_area() in shm_file_operations() unconditional to CONFIG_MMU. As Tony Battersby pointed this can lead NULL-pointer dereference on machine with CONFIG_MMU=y and CONFIG_SHMEM=n. In this case ipc/shm is backed by ramfs which doesn't provide f_op->get_unmapped_area for configurations with MMU. The solution is to provide dummy f_op->get_unmapped_area for ramfs when CONFIG_MMU=y, which just call current->mm->get_unmapped_area(). Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Reported-by: Tony Battersby <tonyb@xxxxxxxxxxxxxxx> Fixes: c01d5b300774 ("shmem: get_unmapped_area align huge page") --- fs/ramfs/file-mmu.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/fs/ramfs/file-mmu.c b/fs/ramfs/file-mmu.c index 183a212694bf..12af0490322f 100644 --- a/fs/ramfs/file-mmu.c +++ b/fs/ramfs/file-mmu.c @@ -27,9 +27,17 @@ #include <linux/fs.h> #include <linux/mm.h> #include <linux/ramfs.h> +#include <linux/sched.h> #include "internal.h" +static unsigned long ramfs_mmu_get_unmapped_area(struct file *file, + unsigned long addr, unsigned long len, unsigned long pgoff, + unsigned long flags) +{ + return current->mm->get_unmapped_area(file, addr, len, pgoff, flags); +} + const struct file_operations ramfs_file_operations = { .read_iter = generic_file_read_iter, .write_iter = generic_file_write_iter, @@ -38,6 +46,7 @@ const struct file_operations ramfs_file_operations = { .splice_read = generic_file_splice_read, .splice_write = iter_file_splice_write, .llseek = generic_file_llseek, + .get_unmapped_area = ramfs_mmu_get_unmapped_area, }; const struct inode_operations ramfs_file_inode_operations = { -- Kirill A. Shutemov -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>