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authorJann Horn <jann@thejh.net>2016-03-22 14:25:36 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-03-22 15:36:02 -0700
commit378c6520e7d29280f400ef2ceaf155c86f05a71a (patch)
treed16654900c79dd882ece48eaaeda3afcffd10e5a /kernel/sysctl_binary.c
parent1333ab03150478df8d6f5673a91df1e50dc6ab97 (diff)
downloadlinux-sh-378c6520e7d29280f400ef2ceaf155c86f05a71a.tar.gz
fs/coredump: prevent fsuid=0 dumps into user-controlled directories
This commit fixes the following security hole affecting systems where all of the following conditions are fulfilled: - The fs.suid_dumpable sysctl is set to 2. - The kernel.core_pattern sysctl's value starts with "/". (Systems where kernel.core_pattern starts with "|/" are not affected.) - Unprivileged user namespace creation is permitted. (This is true on Linux >=3.8, but some distributions disallow it by default using a distro patch.) Under these conditions, if a program executes under secure exec rules, causing it to run with the SUID_DUMP_ROOT flag, then unshares its user namespace, changes its root directory and crashes, the coredump will be written using fsuid=0 and a path derived from kernel.core_pattern - but this path is interpreted relative to the root directory of the process, allowing the attacker to control where a coredump will be written with root privileges. To fix the security issue, always interpret core_pattern for dumps that are written under SUID_DUMP_ROOT relative to the root directory of init. Signed-off-by: Jann Horn <jann@thejh.net> Acked-by: Kees Cook <keescook@chromium.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/sysctl_binary.c')
-rw-r--r--kernel/sysctl_binary.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/sysctl_binary.c b/kernel/sysctl_binary.c
index 7e7746a42a62..10a1d7dc9313 100644
--- a/kernel/sysctl_binary.c
+++ b/kernel/sysctl_binary.c
@@ -1321,7 +1321,7 @@ static ssize_t binary_sysctl(const int *name, int nlen,
}
mnt = task_active_pid_ns(current)->proc_mnt;
- file = file_open_root(mnt->mnt_root, mnt, pathname, flags);
+ file = file_open_root(mnt->mnt_root, mnt, pathname, flags, 0);
result = PTR_ERR(file);
if (IS_ERR(file))
goto out_putname;