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authorChao Yu <chao2.yu@samsung.com>2015-03-23 10:36:15 +0800
committerJaegeuk Kim <jaegeuk@kernel.org>2015-04-10 15:08:53 -0700
commit84e97c2767f9ed711718b47b8722ddd137f1dfe9 (patch)
tree83f8698bd96f0d82bf4f910c39288b6c97a6c625 /fs/f2fs/xattr.c
parentdf6136ef5533421e68ea7ff9c33d5b2ac9005ff9 (diff)
f2fs: avoid NULL pointer dereference in f2fs_xattr_advise_get
We will encounter oops by executing below command. getfattr -n system.advise /mnt/f2fs/file Killed message log: BUG: unable to handle kernel NULL pointer dereference at (null) IP: [<f8b54d69>] f2fs_xattr_advise_get+0x29/0x40 [f2fs] *pdpt = 00000000319b7001 *pde = 0000000000000000 Oops: 0002 [#1] SMP Modules linked in: f2fs(O) snd_intel8x0 snd_ac97_codec ac97_bus snd_pcm snd_seq_midi snd_seq_midi_event snd_rawmidi snd_seq joydev snd_seq_device snd_timer bnep snd rfcomm microcode bluetooth soundcore i2c_piix4 mac_hid serio_raw parport_pc ppdev lp parport binfmt_misc hid_generic psmouse usbhid hid e1000 [last unloaded: f2fs] CPU: 3 PID: 3134 Comm: getfattr Tainted: G O 4.0.0-rc1 #6 Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006 task: f3a71b60 ti: f19a6000 task.ti: f19a6000 EIP: 0060:[<f8b54d69>] EFLAGS: 00010246 CPU: 3 EIP is at f2fs_xattr_advise_get+0x29/0x40 [f2fs] EAX: 00000000 EBX: f19a7e71 ECX: 00000000 EDX: f8b5b467 ESI: 00000000 EDI: f2008570 EBP: f19a7e14 ESP: f19a7e08 DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068 CR0: 80050033 CR2: 00000000 CR3: 319b8000 CR4: 000007f0 Stack: f8b5a634 c0cbb580 00000000 f19a7e34 c1193850 00000000 00000007 f19a7e71 f19a7e64 c0cbb580 c1193810 f19a7e50 c1193c00 00000000 00000000 00000000 c0cbb580 00000000 f19a7f70 c1194097 00000000 00000000 00000000 74737973 Call Trace: [<c1193850>] generic_getxattr+0x40/0x50 [<c1193810>] ? xattr_resolve_name+0x80/0x80 [<c1193c00>] vfs_getxattr+0x70/0xa0 [<c1194097>] getxattr+0x87/0x190 [<c11801d7>] ? path_lookupat+0x57/0x5f0 [<c11819d2>] ? putname+0x32/0x50 [<c116653a>] ? kmem_cache_alloc+0x2a/0x130 [<c11819d2>] ? putname+0x32/0x50 [<c11819d2>] ? putname+0x32/0x50 [<c11819d2>] ? putname+0x32/0x50 [<c11827f9>] ? user_path_at_empty+0x49/0x70 [<c118283f>] ? user_path_at+0x1f/0x30 [<c11941e7>] path_getxattr+0x47/0x80 [<c11948e7>] SyS_getxattr+0x27/0x30 [<c163f748>] sysenter_do_call+0x12/0x12 Code: 66 90 55 89 e5 57 56 53 66 66 66 66 90 8b 78 20 89 d3 ba 67 b4 b5 f8 89 d8 89 ce e8 42 7c 7b c8 85 c0 75 16 0f b6 87 44 01 00 00 <88> 06 b8 01 00 00 00 5b 5e 5f 5d c3 8d 76 00 b8 ea ff ff ff eb EIP: [<f8b54d69>] f2fs_xattr_advise_get+0x29/0x40 [f2fs] SS:ESP 0068:f19a7e08 CR2: 0000000000000000 ---[ end trace 860260654f1f416a ]--- The reason is that in getfattr there are two steps which is indicated by strace info: 1) try to lookup and get size of specified xattr. 2) get value of the extented attribute. strace info: getxattr("/mnt/f2fs/file", "system.advise", 0x0, 0) = 1 getxattr("/mnt/f2fs/file", "system.advise", "\x00", 256) = 1 For the first step, getfattr may pass a NULL pointer in @value and zero in @size as parameters for ->getxattr, but we access this @value pointer directly without checking whether the pointer is valid or not in f2fs_xattr_advise_get, so the oops occurs. This patch fixes this issue by verifying @value pointer before using. Signed-off-by: Chao Yu <chao2.yu@samsung.com> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Diffstat (limited to 'fs/f2fs/xattr.c')
-rw-r--r--fs/f2fs/xattr.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/f2fs/xattr.c b/fs/f2fs/xattr.c
index 5072bf9ae0ef..55649bec0b4d 100644
--- a/fs/f2fs/xattr.c
+++ b/fs/f2fs/xattr.c
@@ -135,7 +135,8 @@ static int f2fs_xattr_advise_get(struct dentry *dentry, const char *name,
if (strcmp(name, "") != 0)
return -EINVAL;
- *((char *)buffer) = F2FS_I(inode)->i_advise;
+ if (buffer)
+ *((char *)buffer) = F2FS_I(inode)->i_advise;
return sizeof(char);
}