On 02/12/2013 07:16 PM, Eric Blake wrote:
On 02/12/2013 01:15 PM, Laine Stump wrote:
If a uid and/or gid is specified for a command, it will be set just after the user-supplied post-fork "hook" function is called.
The intent is that this can replace user hook functions that set uid/gid. This moves the setting of uid/gid and dropping of capabilities closer to each other, which is important since the two should really be done at the same time (libcapng provides a single function that does both, which we will be unable to use, but want to mimic as closely as possible). --- Change from V1: * only bypass uid/gid setting if they are -1 * cast -1 to ([gu]id_t) when comparing to a [gu]id_t * cast uid and gid to (int) for printing
src/libvirt_private.syms | 2 ++ src/util/vircommand.c | 29 +++++++++++++++++++++++++++++ src/util/vircommand.h | 6 +++++- 3 files changed, 36 insertions(+), 1 deletion(-)
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms index b9d45a2..511a686 100644 --- a/src/libvirt_private.syms +++ b/src/libvirt_private.syms @@ -158,12 +158,14 @@ virCommandRun; virCommandRunAsync; virCommandSetErrorBuffer; virCommandSetErrorFD; +virCommandSetGID; virCommandSetInputBuffer; virCommandSetInputFD; virCommandSetOutputBuffer; virCommandSetOutputFD; virCommandSetPidFile; virCommandSetPreExecHook; +virCommandSetUID; Is it common enough to set both gid/uid at once, in order to make this a single function virCommandSetUIDGID?
Well, at the bottom of the call chain, all three operations (setuid, setgid, and set/clear capabilities) have to be done in a single function, but setting capabilities is necessarily a separate function at the higher level because you need to call it multiple times to set multiple capabilities, and it seemed like a natural extension to make setuid and setgid separate functions at this level too; seems to go along with the general philosophy in virCommand of having many separate simple calls, rather than a few really complicated ones.
@@ -605,6 +607,13 @@ virExec(virCommandPtr cmd) goto fork_error; }
+ if (cmd->uid != (uid_t)-1 || cmd->gid != (gid_t)-1) { + VIR_DEBUG("Setting child uid:gid to %d:%d", + (int)cmd->uid, (int)cmd->gid); + if (virSetUIDGID(cmd->uid, cmd->gid) < 0) In fact, down at a lower layer in the stack, we pass both ids at once.
Hmm, in the chown() case, doing both at once lets you use one syscall instead of two; but in the set*id() functions, it's separate syscalls for uid vs. gid no matter what we do, so I guess it doesn't really matter whether it is two separate calls or one combined call higher up in the stack. But what you have with separate calls works, so I don't mind whether you keep it as-is, to save the hassle of rippling a combined call through the rest of the series.
ACK.