From 42a0cc3478584d4d63f68f2f5af021ddbea771fa Mon Sep 17 00:00:00 2001 From: Jann Horn Date: Mon, 25 Jun 2018 18:34:10 +0200 Subject: sys: don't hold uts_sem while accessing userspace memory Holding uts_sem as a writer while accessing userspace memory allows a namespace admin to stall all processes that attempt to take uts_sem. Instead, move data through stack buffers and don't access userspace memory while uts_sem is held. Cc: stable@vger.kernel.org Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Jann Horn Signed-off-by: Eric W. Biederman --- arch/alpha/kernel/osf_sys.c | 51 +++++++++++++++++++++------------------------ 1 file changed, 24 insertions(+), 27 deletions(-) (limited to 'arch/alpha') diff --git a/arch/alpha/kernel/osf_sys.c b/arch/alpha/kernel/osf_sys.c index 6e921754c8fc..2a5c768df335 100644 --- a/arch/alpha/kernel/osf_sys.c +++ b/arch/alpha/kernel/osf_sys.c @@ -530,24 +530,19 @@ SYSCALL_DEFINE4(osf_mount, unsigned long, typenr, const char __user *, path, SYSCALL_DEFINE1(osf_utsname, char __user *, name) { int error; + char tmp[5 * 32]; down_read(&uts_sem); - error = -EFAULT; - if (copy_to_user(name + 0, utsname()->sysname, 32)) - goto out; - if (copy_to_user(name + 32, utsname()->nodename, 32)) - goto out; - if (copy_to_user(name + 64, utsname()->release, 32)) - goto out; - if (copy_to_user(name + 96, utsname()->version, 32)) - goto out; - if (copy_to_user(name + 128, utsname()->machine, 32)) - goto out; + memcpy(tmp + 0 * 32, utsname()->sysname, 32); + memcpy(tmp + 1 * 32, utsname()->nodename, 32); + memcpy(tmp + 2 * 32, utsname()->release, 32); + memcpy(tmp + 3 * 32, utsname()->version, 32); + memcpy(tmp + 4 * 32, utsname()->machine, 32); + up_read(&uts_sem); - error = 0; - out: - up_read(&uts_sem); - return error; + if (copy_to_user(name, tmp, sizeof(tmp))) + return -EFAULT; + return 0; } SYSCALL_DEFINE0(getpagesize) @@ -567,18 +562,21 @@ SYSCALL_DEFINE2(osf_getdomainname, char __user *, name, int, namelen) { int len, err = 0; char *kname; + char tmp[32]; - if (namelen > 32) + if (namelen < 0 || namelen > 32) namelen = 32; down_read(&uts_sem); kname = utsname()->domainname; len = strnlen(kname, namelen); - if (copy_to_user(name, kname, min(len + 1, namelen))) - err = -EFAULT; + len = min(len + 1, namelen); + memcpy(tmp, kname, len); up_read(&uts_sem); - return err; + if (copy_to_user(name, tmp, len)) + return -EFAULT; + return 0; } /* @@ -739,13 +737,14 @@ SYSCALL_DEFINE3(osf_sysinfo, int, command, char __user *, buf, long, count) }; unsigned long offset; const char *res; - long len, err = -EINVAL; + long len; + char tmp[__NEW_UTS_LEN + 1]; offset = command-1; if (offset >= ARRAY_SIZE(sysinfo_table)) { /* Digital UNIX has a few unpublished interfaces here */ printk("sysinfo(%d)", command); - goto out; + return -EINVAL; } down_read(&uts_sem); @@ -753,13 +752,11 @@ SYSCALL_DEFINE3(osf_sysinfo, int, command, char __user *, buf, long, count) len = strlen(res)+1; if ((unsigned long)len > (unsigned long)count) len = count; - if (copy_to_user(buf, res, len)) - err = -EFAULT; - else - err = 0; + memcpy(tmp, res, len); up_read(&uts_sem); - out: - return err; + if (copy_to_user(buf, tmp, len)) + return -EFAULT; + return 0; } SYSCALL_DEFINE5(osf_getsysinfo, unsigned long, op, void __user *, buffer, -- cgit