On Fri, 2020-04-24 at 15:52 +0200, Solar Designer wrote: > On Fri, Apr 24, 2020 at 12:07:15AM +0100, Ben Hutchings wrote: > > 3.16.83-rc1 review patch. If anyone has any objections, please let me know. > > I do. This patch is currently known-buggy, see this thread: > > https://www.openwall.com/lists/oss-security/2020/01/28/2 > > It is (partially) fixed with these newer commits in 5.5 and 5.5.2: > > commit d0cb50185ae942b03c4327be322055d622dc79f6 > Author: Al Viro <viro@xxxxxxxxxxxxxxxxxx> > Date: Sun Jan 26 09:29:34 2020 -0500 > > do_last(): fetch directory ->i_mode and ->i_uid before it's too late > > may_create_in_sticky() call is done when we already have dropped the > reference to dir. > > Fixes: 30aba6656f61e (namei: allow restricted O_CREAT of FIFOs and regular files) > Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx> > > commit d76341d93dedbcf6ed5a08dfc8bce82d3e9a772b > Author: Al Viro <viro@xxxxxxxxxxxxxxxxxx> > Date: Sat Feb 1 16:26:45 2020 +0000 > > vfs: fix do_last() regression > > commit 6404674acd596de41fd3ad5f267b4525494a891a upstream. [...] > At least inclusion of the above fixes is mandatory for any backports. I know, and those are the next 2 patches in the series. > Also, I think no one has fixed the logic of may_create_in_sticky() so > that it wouldn't unintentionally apply the "protection" when the file > is neither a FIFO nor a regular file (something I found and mentioned in > the oss-security posting above). [...] > I think the implementation of may_create_in_sticky() should be rewritten > such that it'd directly correspond to the textual description in the > comment above. As we've seen, trying to write the code "more optimally" > resulted in its logic actually being different from the description. > > Meanwhile, I think backporting known-so-buggy code is a bad idea. I can see that it's not quite right, but does it matter in practice? Directories and symlinks are handled separately; sockets can't be opened anyway; block and character devices wonn't normally appear in a sticky directory. Ben. -- Ben Hutchings Knowledge is power. France is bacon.
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