[PATCH 23/24] sys:__sys_setresgid(): handle fsid mappings
From: Christian Brauner <hidden>
Date: 2020-02-11 17:02:27
Also in:
linux-fsdevel, linux-security-module, lkml
Subsystem:
the rest · Maintainer:
Linus Torvalds
Switch setresgid() to lookup fsids in the fsid mappings. If no fsid mappings are setup the behavior is unchanged, i.e. fsids are looked up in the id mappings. During setresgid() the kfsgid is set to the kegid corresponding the egid that is requested by userspace. If the requested egid is -1 the kfsgid is reset to the current kegid. For the latter case this means we need to lookup the corresponding userspace egid corresponding to the current kegid in the id mappings and translate this egid into the corresponding kfsgid in the fsid mappings. Signed-off-by: Christian Brauner <redacted> --- kernel/sys.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/kernel/sys.c b/kernel/sys.c
index 3b98ce84607d..674d0ba4887c 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c@@ -750,11 +750,12 @@ long __sys_setresgid(gid_t rgid, gid_t egid, gid_t sgid) const struct cred *old; struct cred *new; int retval; - kgid_t krgid, kegid, ksgid; + kgid_t krgid, kegid, ksgid, kfsgid; krgid = make_kgid(ns, rgid); kegid = make_kgid(ns, egid); ksgid = make_kgid(ns, sgid); + kfsgid = make_kfsgid(ns, egid); if ((rgid != (gid_t) -1) && !gid_valid(krgid)) return -EINVAL;
@@ -762,6 +763,8 @@ long __sys_setresgid(gid_t rgid, gid_t egid, gid_t sgid) return -EINVAL; if ((sgid != (gid_t) -1) && !gid_valid(ksgid)) return -EINVAL; + if ((egid != (gid_t) -1) && !gid_valid(kfsgid)) + return -EINVAL; new = prepare_creds(); if (!new)
@@ -783,11 +786,15 @@ long __sys_setresgid(gid_t rgid, gid_t egid, gid_t sgid) if (rgid != (gid_t) -1) new->gid = krgid; - if (egid != (gid_t) -1) + if (egid != (gid_t) -1) { new->egid = kegid; + } else { + gid_t fsgid = from_kgid_munged(new->user_ns, new->egid); + kfsgid = make_kfsgid(ns, fsgid); + } if (sgid != (gid_t) -1) new->sgid = ksgid; - new->fsgid = new->egid; + new->fsgid = kfsgid; return commit_creds(new);
--
2.25.0