| Message ID | 20200607234118.e6OahXAr8%akpm@linux-foundation.org |
|---|---|
| State | New |
| Headers | show |
| Series | + nilfs2-fix-null-pointer-dereference-at-nilfs_segctor_do_construct.patch added to -mm tree | expand |
--- a/fs/nilfs2/segment.c~nilfs2-fix-null-pointer-dereference-at-nilfs_segctor_do_construct +++ a/fs/nilfs2/segment.c @@ -2780,6 +2780,8 @@ int nilfs_attach_log_writer(struct super if (!nilfs->ns_writer) return -ENOMEM; + inode_attach_wb(nilfs->ns_bdev->bd_inode, NULL); + err = nilfs_segctor_start_thread(nilfs->ns_writer); if (err) { kfree(nilfs->ns_writer);
The patch titled Subject: nilfs2: fix null pointer dereference at nilfs_segctor_do_construct() has been added to the -mm tree. Its filename is nilfs2-fix-null-pointer-dereference-at-nilfs_segctor_do_construct.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/nilfs2-fix-null-pointer-dereference-at-nilfs_segctor_do_construct.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/nilfs2-fix-null-pointer-dereference-at-nilfs_segctor_do_construct.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Ryusuke Konishi <konishi.ryusuke@gmail.com> Subject: nilfs2: fix null pointer dereference at nilfs_segctor_do_construct() After commit c3aab9a0bd91 ("mm/filemap.c: don't initiate writeback if mapping has no dirty pages"), the following null pointer dereference has been reported on nilfs2: BUG: kernel NULL pointer dereference, address: 00000000000000a8 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] SMP PTI ... RIP: 0010:percpu_counter_add_batch+0xa/0x60 ... Call Trace: __test_set_page_writeback+0x2d3/0x330 nilfs_segctor_do_construct+0x10d3/0x2110 [nilfs2] nilfs_segctor_construct+0x168/0x260 [nilfs2] nilfs_segctor_thread+0x127/0x3b0 [nilfs2] kthread+0xf8/0x130 ... This crash turned out to be caused by set_page_writeback() call for segment summary buffers at nilfs_segctor_prepare_write(). set_page_writeback() can call inc_wb_stat(inode_to_wb(inode), WB_WRITEBACK) where inode_to_wb(inode) is NULL if the inode of underlying block device does not have an associated wb. This fixes the issue by calling inode_attach_wb() in advance to ensure to associate the bdev inode with its wb. Link: http://lkml.kernel.org/r/20200608.011819.1399059588922299158.konishi.ryusuke@gmail.com Fixes: c3aab9a0bd91 ("mm/filemap.c: don't initiate writeback if mapping has no dirty pages") Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com> Tested-by: Ryusuke Konishi <konishi.ryusuke@gmail.com> Reported-by: Walton Hoops <me@waltonhoops.com> Reported-by: Tomas Hlavaty <tom@logand.com> Reported-by: ARAI Shun-ichi <hermes@ceres.dti.ne.jp> Reported-by: Hideki EIRAKU <hdk1983@gmail.com> Cc: <stable@vger.kernel.org> [5.4+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> --- fs/nilfs2/segment.c | 2 ++ 1 file changed, 2 insertions(+)