Messages in this thread Patch in this message | | | From | BlaisorBlade <> | Subject | [PATCH] Missing BKL in sys_chroot() for 2.6 | Date | Sun, 6 Jun 2004 19:58:48 +0200 |
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(PLEASE cc me on replies as I'm not subscribed).
Set_fs_root *claims* it wants the BKL held:
/* * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values. * It can block. Requires the big lock held. */ void set_fs_root(struct fs_struct *fs, struct vfsmount *mnt, struct dentry *dentry)
But sys_chroot ignores this. So I attach this patch (apply with patch -p1 -l). Maybe the solution is to kill that comment, maybe not (sys_pivot_root() calls chroot_fs_refs() -> set_fs_root() with the BKL held, but that has a lot of reasons other than this). If that comment is correct, however, it probably holds even for set_fs_altroot(), since it's similar. So this patch adds it.
TESTING: none, I'm sure about the inconsistency, a lot less about the solution (no kernel manual explains the BKL, since it is a relict; except the ones who still says it blocks all the rest of the kernel, while I think it is just a recursive and "sleepable" spinlock - am I correct?).
--- vanilla-linux-2.6.6/fs/open.c.saved 2004-05-10 21:37:11.000000000 +0200 +++ vanilla-linux-2.6.6/fs/open.c 2004-06-06 19:40:20.000000000 +0200 @@ -581,8 +581,13 @@ if (!capable(CAP_SYS_CHROOT)) goto dput_and_out;
+ lock_kernel(); + set_fs_root(current->fs, nd.mnt, nd.dentry); set_fs_altroot(); + + unlock_kernel(); + error = 0; dput_and_out: path_release(&nd); --- vanilla-linux-2.6.6/fs/namei.c.saved 2004-05-10 21:37:09.000000000 +0200 +++ vanilla-linux-2.6.6/fs/namei.c 2004-06-06 19:49:25.000000000 +0200 @@ -814,6 +814,9 @@ return 1; }
+/* + * Requires the big lock held. + */ void set_fs_altroot(void) { char *emul = __emul_prefix(); -- Paolo Giarrusso, aka Blaisorblade Linux registered user n. 292729
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