On Mon, Aug 29, 2022 at 10:52:57AM -0700, Jaegeuk Kim wrote: > On 08/25, Andrew Morton wrote: > > (cc fsf2 developers) > > > > On Thu, 25 Aug 2022 08:29:32 -0700 syzbot <syzbot+775a3440817f74fddb8c@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > > > > Hello, > > > > > > syzbot found the following issue on: > > > > > > HEAD commit: a41a877bc12d Merge branch 'for-next/fixes' into for-kernelci > > > git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci > > > console output: https://syzkaller.appspot.com/x/log.txt?x=175def47080000 > > > kernel config: https://syzkaller.appspot.com/x/.config?x=5cea15779c42821c > > > dashboard link: https://syzkaller.appspot.com/bug?extid=775a3440817f74fddb8c > > > compiler: Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2 > > > userspace arch: arm64 > > > > > > Unfortunately, I don't have any reproducer for this issue yet. > > > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > > Reported-by: syzbot+775a3440817f74fddb8c@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > > > Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 > > > Mem abort info: > > > ESR = 0x0000000086000005 > > > EC = 0x21: IABT (current EL), IL = 32 bits > > > SET = 0, FnV = 0 > > > EA = 0, S1PTW = 0 > > > FSC = 0x05: level 1 translation fault > > > user pgtable: 4k pages, 48-bit VAs, pgdp=00000001249cc000 > > > [0000000000000000] pgd=080000012ee65003, p4d=080000012ee65003, pud=0000000000000000 > > > Internal error: Oops: 86000005 [#1] PREEMPT SMP > > > Modules linked in: > > > CPU: 0 PID: 3044 Comm: syz-executor.0 Not tainted 6.0.0-rc2-syzkaller-16455-ga41a877bc12d #0 > > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/20/2022 > > > pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) > > > pc : 0x0 > > > lr : folio_mark_dirty+0xbc/0x208 mm/page-writeback.c:2748 > > > sp : ffff800012803830 > > > x29: ffff800012803830 x28: ffff0000d02c8000 x27: 0000000000000009 > > > x26: 0000000000000001 x25: 0000000000000a00 x24: 0000000000000080 > > > x23: 0000000000000000 x22: ffff0000ef276c00 x21: 05ffc00000000007 > > > x20: ffff0000f14b83b8 x19: fffffc00036409c0 x18: fffffffffffffff5 > > > x17: ffff80000dd7a698 x16: ffff80000dbb8658 x15: 0000000000000000 > > > x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000 > > > x11: ff808000083e9814 x10: 0000000000000000 x9 : ffff8000083e9814 > > > x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000 > > > x5 : ffff0000d9028000 x4 : ffff0000d5c31000 x3 : ffff0000d9027f80 > > > x2 : fffffffffffffff0 x1 : fffffc00036409c0 x0 : ffff0000f14b83b8 > > > Call trace: > > > 0x0 > > > set_page_dirty+0x38/0xbc mm/folio-compat.c:62 > > 2363 void f2fs_update_meta_page(struct f2fs_sb_info *sbi, > 2364 void *src, block_t blk_addr) > 2365 { > 2366 struct page *page = f2fs_grab_meta_page(sbi, blk_addr); > > --> f2fs_grab_meta_page() gives a locked page by grab_cache_page(). > > 2367 > 2368 memcpy(page_address(page), src, PAGE_SIZE); > 2369 set_page_dirty(page); > 2370 f2fs_put_page(page, 1); > 2371 } > > Is there a change in folio? Not directly, but there was a related change, 0af573780b0b which requires aops->set_page_dirty to be set; is that perhaps missing? I don't see one in the f2fs_compress_aops, for example. The other possibiity is that it's a mapping that is missing an ->a_ops. Is that something f2fs ever does? I only managed to narrow down the crash to the line: return mapping->a_ops->dirty_folio(mapping, folio); so either mapping->a_ops is NULL or mapping->a_ops->dirty_folio is NULL. The reproducer was on ARM and ARM doesn't emit a 'Code:' line, unlike x86.
