Hello and thanks for the patch! On 2014-07-24 17:25:42, Chao Yu wrote: > https://bugzilla.kernel.org/show_bug.cgi?id=41692 This actually isn't the bug that this patch fixes. It is a different bug (that I don't think exists anymore) and someone happened to test for the bug on a newer kernel and hit the oops that you're fixing here. > > Christopher Head 2014-06-28 05:26:20 UTC described: > "I tried to reproduce this on 3.12.21. Instead, when I do "echo hello > foo" > in an ecryptfs mount with ecryptfs_xattr specified, I get a kernel crash: > > BUG: unable to handle kernel NULL pointer dereference at (null) > IP: [<ffffffff8110eb39>] fsstack_copy_attr_all+0x2/0x61 > PGD d7840067 PUD b2c3c067 PMD 0 > Oops: 0002 [#1] SMP > Modules linked in: nvidia(PO) > CPU: 3 PID: 3566 Comm: bash Tainted: P O 3.12.21-gentoo-r1 #2 > Hardware name: ASUSTek Computer Inc. G60JX/G60JX, BIOS 206 03/15/2010 > task: ffff8801948944c0 ti: ffff8800bad70000 task.ti: ffff8800bad70000 > RIP: 0010:[<ffffffff8110eb39>] [<ffffffff8110eb39>] fsstack_copy_attr_all+0x2/0x61 > RSP: 0018:ffff8800bad71c10 EFLAGS: 00010246 > RAX: 00000000000181a4 RBX: ffff880198648480 RCX: 0000000000000000 > RDX: 0000000000000004 RSI: ffff880172010450 RDI: 0000000000000000 > RBP: ffff880198490e40 R08: 0000000000000000 R09: 0000000000000000 > R10: ffff880172010450 R11: ffffea0002c51e80 R12: 0000000000002000 > R13: 000000000000001a R14: 0000000000000000 R15: ffff880198490e40 > FS: 00007ff224caa700(0000) GS:ffff88019fcc0000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000000000000 CR3: 00000000bb07f000 CR4: 00000000000007e0 > Stack: > ffffffff811826e8 ffff8800a39d8000 0000000000000000 000000000000001a > ffff8800a01d0000 ffff8800a39d8000 ffffffff81185fd5 ffffffff81082c2c > 00000001a39d8000 53d0abbc98490e40 0000000000000037 ffff8800a39d8220 > Call Trace: > [<ffffffff811826e8>] ? ecryptfs_setxattr+0x40/0x52 > [<ffffffff81185fd5>] ? ecryptfs_write_metadata+0x1b3/0x223 > [<ffffffff81082c2c>] ? should_resched+0x5/0x23 > [<ffffffff8118322b>] ? ecryptfs_initialize_file+0xaf/0xd4 > [<ffffffff81183344>] ? ecryptfs_create+0xf4/0x142 > [<ffffffff810f8c0d>] ? vfs_create+0x48/0x71 > [<ffffffff810f9c86>] ? do_last.isra.68+0x559/0x952 > [<ffffffff810f7ce7>] ? link_path_walk+0xbd/0x458 > [<ffffffff810fa2a3>] ? path_openat+0x224/0x472 > [<ffffffff810fa7bd>] ? do_filp_open+0x2b/0x6f > [<ffffffff81103606>] ? __alloc_fd+0xd6/0xe7 > [<ffffffff810ee6ab>] ? do_sys_open+0x65/0xe9 > [<ffffffff8157d022>] ? system_call_fastpath+0x16/0x1b > RIP [<ffffffff8110eb39>] fsstack_copy_attr_all+0x2/0x61 > RSP <ffff8800bad71c10> > CR2: 0000000000000000 > ---[ end trace df9dba5f1ddb8565 ]---" > > If we create a file when we mount with ecryptfs_xattr_metadata option, we will > encounter a crash in this path: > ->ecryptfs_create > ->ecryptfs_initialize_file > ->ecryptfs_write_metadata > ->ecryptfs_write_metadata_to_xattr > ->ecryptfs_setxattr > ->fsstack_copy_attr_all > It's because our dentry->d_inode used in fsstack_copy_attr_all is NULL, and it > will be initialized when ecryptfs_initialize_file finish. > > So we should skip copying attr from lower inode when the value of ->d_inode is > invalid. > > Signed-off-by: Chao Yu <chao2.yu@xxxxxxxxxxx> > --- I wrote a patch to fix this bug last week, made the changes necessary to run through all of the eCryptfs tests with the ecryptfs_xattr_metadata mount option, tested the fix, and then forgot to send out the patch. (doh!) But it worked out well because I think I like your patch better. I moved the innards of ecryptfs_setxattr() into a new function that accepts the lower_dentry and ecryptfs inode as separate arguments. That way it can work regardless of the eCryptfs dentry not yet being d_initialized(). After looking at your patch, I don't think that's necessary. Skipping the fsstack_copy_attr_all() should be fine for brand new eCryptfs inodes since the attr copy just happened in ecryptfs_inode_set(). I'll test your patch and then push it to the eCryptfs -next branch. I'll also update the bug link to point to the specific comment rather than the unrelated bug itself. Thanks! Tyler > fs/ecryptfs/inode.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c > index e67f9f0..436b7d8 100644 > --- a/fs/ecryptfs/inode.c > +++ b/fs/ecryptfs/inode.c > @@ -1037,7 +1037,7 @@ ecryptfs_setxattr(struct dentry *dentry, const char *name, const void *value, > } > > rc = vfs_setxattr(lower_dentry, name, value, size, flags); > - if (!rc) > + if (!rc && dentry->d_inode) > fsstack_copy_attr_all(dentry->d_inode, lower_dentry->d_inode); > out: > return rc; > -- > 2.0.1.474.g72c7794 > >
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