From 54d71856428961124be26301b7997f2ad23be520 Mon Sep 17 00:00:00 2001 From: Chao Yu Date: Fri, 28 Aug 2015 18:18:57 +0800 Subject: f2fs: avoid accessing NULL pointer in f2fs_drop_largest_extent If extent cache is disable, we will encounter oops when triggering direct IO as below: BUG: unable to handle kernel NULL pointer dereference at 0000000c IP: [] f2fs_drop_largest_extent+0xe/0x30 [f2fs] *pdpt = 000000002bb9a001 *pde = 0000000000000000 Oops: 0000 [#1] SMP Modules linked in: f2fs(O) fuse bnep rfcomm bluetooth nfsd dm_crypt nfs_acl auth_rpcgss oid_registry nfs binfmt_misc fscache lockd sunrpc grace snd_intel8x0 snd_ac97_codec ac97_bus snd_pcm snd_seq_midi snd_rawmidi snd_seq_midi_event snd_seq snd_timer snd_seq_device snd soundcore joydev psmouse hid_generic i2c_piix4 serio_raw ppdev mac_hid parport_pc lp parport ext4 jbd2 mbcache usbhid hid e1000 CPU: 3 PID: 3608 Comm: dd Tainted: G O 4.2.0-rc4 #12 Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006 task: ef161600 ti: ebd5e000 task.ti: ebd5e000 EIP: 0060:[] EFLAGS: 00010202 CPU: 3 EIP is at f2fs_drop_largest_extent+0xe/0x30 [f2fs] EAX: 00000000 EBX: ddebc000 ECX: 00000000 EDX: 00000000 ESI: ebd5fdf8 EDI: 00000000 EBP: ebd5fd58 ESP: ebd5fd58 DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068 CR0: 80050033 CR2: 0000000c CR3: 2c24ee40 CR4: 000006f0 Stack: ebd5fda4 f0b8c005 00000000 00000001 00000000 f0b8c430 c816cd68 ddebc000 ddebc088 00001000 00000555 00000555 ffffffff c160bb00 00055501 00000000 00000000 00000100 00000000 ebd5fe20 f0b8c430 00000046 ef161600 00001000 Call Trace: [] __allocate_data_block+0x1a5/0x260 [f2fs] [] ? f2fs_direct_IO+0x370/0x440 [f2fs] [] ? down_read+0x30/0x50 [] f2fs_direct_IO+0x370/0x440 [f2fs] [] generic_file_direct_write+0xa5/0x260 [] ? current_fs_time+0x18/0x50 [] __generic_file_write_iter+0xbb/0x210 [] ? generic_file_write_iter+0x2f/0x320 [] generic_file_write_iter+0x15c/0x320 [] f2fs_file_write_iter+0x39/0x80 [f2fs] [] __vfs_write+0xa9/0xe0 [] vfs_write+0x97/0x180 [] SyS_write+0x5b/0xd0 [] sysenter_do_call+0x12/0x12 Code: 10 8b 50 1c 89 53 14 eb ca 8d 74 26 00 85 f6 74 86 eb a6 0f 0b 90 8d b4 26 00 00 00 00 55 89 e5 3e 8d 74 26 00 8b 80 d4 02 00 00 <8b> 48 0c 39 d1 77 0e 03 48 14 39 ca 73 07 c7 40 14 00 00 00 00 EIP: [] f2fs_drop_largest_extent+0xe/0x30 [f2fs] SS:ESP 0068:ebd5fd58 CR2: 000000000000000c ---[ end trace a38c07026a1afffd ]--- This is because when extent cache is disable, extent_tree pointer in struct f2fs_inode_info should be NULL, but in f2fs_drop_largest_extent we access this NULL pointer directly without checking state of extent cache, then, the oops occurs. Let's fix it by checking state of extent cache before accessing. Signed-off-by: Chao Yu Signed-off-by: Jaegeuk Kim --- fs/f2fs/extent_cache.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) (limited to 'fs') diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c index e6b245718ef0..997ac86f2a1d 100644 --- a/fs/f2fs/extent_cache.c +++ b/fs/f2fs/extent_cache.c @@ -155,7 +155,7 @@ static unsigned int __free_extent_tree(struct f2fs_sb_info *sbi, return count - et->count; } -void f2fs_drop_largest_extent(struct inode *inode, pgoff_t fofs) +static void __drop_largest_extent(struct inode *inode, pgoff_t fofs) { struct extent_info *largest = &F2FS_I(inode)->extent_tree->largest; @@ -163,6 +163,14 @@ void f2fs_drop_largest_extent(struct inode *inode, pgoff_t fofs) largest->len = 0; } +void f2fs_drop_largest_extent(struct inode *inode, pgoff_t fofs) +{ + if (!f2fs_may_extent_tree(inode)) + return; + + __drop_largest_extent(inode, fofs); +} + void f2fs_init_extent_tree(struct inode *inode, struct f2fs_extent *i_ext) { struct f2fs_sb_info *sbi = F2FS_I_SB(inode); @@ -412,7 +420,7 @@ unsigned int f2fs_update_extent_tree_range(struct inode *inode, dei.len = 0; /* we do not guarantee that the largest extent is cached all the time */ - f2fs_drop_largest_extent(inode, fofs); + __drop_largest_extent(inode, fofs); /* 1. lookup first extent node in range [fofs, fofs + len - 1] */ en = __lookup_extent_tree_ret(et, fofs, &prev_en, &next_en, -- cgit v1.2.3-59-g8ed1b