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Re: [RFC] Possible new execveat(2) Linux syscall
- From: Christoph Hellwig <hch at infradead dot org>
- To: Rich Felker <dalias at aerifal dot cx>
- Cc: David Drysdale <drysdale at google dot com>, libc-alpha at sourceware dot org, Andrew Morton <akpm at linux-foundation dot org>, Christoph Hellwig <hch at infradead dot org>, Linux API <linux-api at vger dot kernel dot org>, Andy Lutomirski <luto at amacapital dot net>, musl at lists dot openwall dot com
- Date: Fri, 21 Nov 2014 02:13:18 -0800
- Subject: Re: [RFC] Possible new execveat(2) Linux syscall
- Authentication-results: sourceware.org; auth=none
- References: <CAHse=S8ccC2No5EYS0Pex=Ng3oXjfDB9woOBmMY_k+EgxtODZA at mail dot gmail dot com> <20141116195246 dot GX22465 at brightrain dot aerifal dot cx>
On Sun, Nov 16, 2014 at 02:52:46PM -0500, Rich Felker wrote:
> I've been following the discussions so far and everything looks mostly
> okay. There are still issues to be resolved with the different
> semantics between Linux O_PATH and what POSIX requires for O_EXEC (and
> O_SEARCH) but as long as the intent is that, once O_EXEC is defined to
> save the permissions at the time of open and cause them to be used in
> place of the current file permissions at the time of execveat
As far as I can tell we only need the little patch below to make Linux
O_PATH a valid O_SEARCH implementation. Rich, you said you wanted to
look over it?
For O_EXEC my interpretation is that we basically just need this new
execveat syscall + a patch to add FMODE_EXEC and enforce it. So we
wouldn't even need the O_PATH|3 hack. But unless someone more familar
with the arcane details of the Posix language verifies it I'm tempted to
give up trying to help to implent these flags :(
diff --git a/fs/open.c b/fs/open.c
index d6fd3ac..ee24720 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -512,7 +512,7 @@ out_unlock:
SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
{
- struct fd f = fdget(fd);
+ struct fd f = fdget_raw(fd);
int err = -EBADF;
if (f.file) {
@@ -633,7 +633,7 @@ SYSCALL_DEFINE3(lchown, const char __user *, filename, uid_t, user, gid_t, group
SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
{
- struct fd f = fdget(fd);
+ struct fd f = fdget_raw(fd);
int error = -EBADF;
if (!f.file)