From: Josef Bacik josef@toxicpanda.com
[ Upstream commit 719fcafe07c12646691bd62d7f8d94d657fa0766 ]
We've been seeing the following panic in production
BUG: kernel NULL pointer dereference, address: 0000000000000065 PGD 2f485f067 P4D 2f485f067 PUD 2cc5d8067 PMD 0 RIP: 0010:ff_layout_cancel_io+0x3a/0x90 [nfs_layout_flexfiles] Call Trace: <TASK> ? __die+0x78/0xc0 ? page_fault_oops+0x286/0x380 ? __rpc_execute+0x2c3/0x470 [sunrpc] ? rpc_new_task+0x42/0x1c0 [sunrpc] ? exc_page_fault+0x5d/0x110 ? asm_exc_page_fault+0x22/0x30 ? ff_layout_free_layoutreturn+0x110/0x110 [nfs_layout_flexfiles] ? ff_layout_cancel_io+0x3a/0x90 [nfs_layout_flexfiles] ? ff_layout_cancel_io+0x6f/0x90 [nfs_layout_flexfiles] pnfs_mark_matching_lsegs_return+0x1b0/0x360 [nfsv4] pnfs_error_mark_layout_for_return+0x9e/0x110 [nfsv4] ? ff_layout_send_layouterror+0x50/0x160 [nfs_layout_flexfiles] nfs4_ff_layout_prepare_ds+0x11f/0x290 [nfs_layout_flexfiles] ff_layout_pg_init_write+0xf0/0x1f0 [nfs_layout_flexfiles] __nfs_pageio_add_request+0x154/0x6c0 [nfs] nfs_pageio_add_request+0x26b/0x380 [nfs] nfs_do_writepage+0x111/0x1e0 [nfs] nfs_writepages_callback+0xf/0x30 [nfs] write_cache_pages+0x17f/0x380 ? nfs_pageio_init_write+0x50/0x50 [nfs] ? nfs_writepages+0x6d/0x210 [nfs] ? nfs_writepages+0x6d/0x210 [nfs] nfs_writepages+0x125/0x210 [nfs] do_writepages+0x67/0x220 ? generic_perform_write+0x14b/0x210 filemap_fdatawrite_wbc+0x5b/0x80 file_write_and_wait_range+0x6d/0xc0 nfs_file_fsync+0x81/0x170 [nfs] ? nfs_file_mmap+0x60/0x60 [nfs] __x64_sys_fsync+0x53/0x90 do_syscall_64+0x3d/0x90 entry_SYSCALL_64_after_hwframe+0x46/0xb0
Inspecting the core with drgn I was able to pull this
prog.crashed_thread().stack_trace()[0]
#0 at 0xffffffffa079657a (ff_layout_cancel_io+0x3a/0x84) in ff_layout_cancel_io at fs/nfs/flexfilelayout/flexfilelayout.c:2021:27
prog.crashed_thread().stack_trace()[0]['idx']
(u32)1
prog.crashed_thread().stack_trace()[0]['flseg'].mirror_array[1].mirror_ds
(struct nfs4_ff_layout_ds *)0xffffffffffffffed
This is clear from the stack trace, we call nfs4_ff_layout_prepare_ds() which could error out initializing the mirror_ds, and then we go to clean it all up and our check is only for if (!mirror->mirror_ds). This is inconsistent with the rest of the users of mirror_ds, which have
if (IS_ERR_OR_NULL(mirror_ds))
to keep from tripping over this exact scenario. Fix this up in ff_layout_cancel_io() to make sure we don't panic when we get an error. I also spot checked all the other instances of checking mirror_ds and we appear to be doing the correct checks everywhere, only unconditionally dereferencing mirror_ds when we know it would be valid.
Signed-off-by: Josef Bacik josef@toxicpanda.com Fixes: b739a5bd9d9f ("NFSv4/flexfiles: Cancel I/O if the layout is recalled or revoked") Reviewed-by: Jeff Layton jlayton@kernel.org Signed-off-by: Trond Myklebust trond.myklebust@hammerspace.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/nfs/flexfilelayout/flexfilelayout.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/nfs/flexfilelayout/flexfilelayout.c b/fs/nfs/flexfilelayout/flexfilelayout.c index 81bbafab18a99..4376881be7918 100644 --- a/fs/nfs/flexfilelayout/flexfilelayout.c +++ b/fs/nfs/flexfilelayout/flexfilelayout.c @@ -2016,7 +2016,7 @@ static void ff_layout_cancel_io(struct pnfs_layout_segment *lseg) for (idx = 0; idx < flseg->mirror_array_cnt; idx++) { mirror = flseg->mirror_array[idx]; mirror_ds = mirror->mirror_ds; - if (!mirror_ds) + if (IS_ERR_OR_NULL(mirror_ds)) continue; ds = mirror->mirror_ds->ds; if (!ds)