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author | Denys Vlasenko <vda.linux@googlemail.com> | 2017-07-10 09:17:43 +0200 |
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committer | Denys Vlasenko <vda.linux@googlemail.com> | 2017-07-10 09:17:43 +0200 |
commit | 12a4f9afe702b89c616610d3a29bf08257c6bace (patch) | |
tree | bad36f9bd86ae61bf188186eab53c636b179dd67 /shell/hush.c | |
parent | 9de9c871bf44b931c7a1bb66d3134e2deb811f88 (diff) | |
download | busybox-12a4f9afe702b89c616610d3a29bf08257c6bace.tar.gz |
libbb: do not die if setgid/setuid(real_id) on startup fails
Based on a patch from Steven McDonald <steven@steven-mcdonald.id.au>:
This makes 'unshare --user' work correctly in the case where the user's
shell is provided by busybox itself.
'unshare --user' creates a new user namespace without any uid mappings.
As a result, /bin/busybox is setuid nobody:nogroup within the
namespace, as that is the only user. However, since no uids are mapped,
attempting to call setgid/setuid fails, even though this would do
nothing:
$ unshare --user ./busybox.broken ash
ash: setgid: Invalid argument
'unshare --map-root-user' still works, but because Linux only allows
uid/gid mappings to be set up once, creating a root mapping makes such
a namespace useless for creating multi-user containers.
With this patch, setgid and setuid will not be called in the case where
they would do nothing, which is always the case inside a new user
namespace because all uids are effectively mapped to nobody:
$ id -u
1000
$ ls -lh busybox.fixed
-rwsr-xr-x 1 root root 826.2K May 21 00:33 busybox.fixed
$ unshare --user ./busybox.fixed ash
$ id -u
65534
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Diffstat (limited to 'shell/hush.c')
0 files changed, 0 insertions, 0 deletions