[REVIEW][PATCH 7/6] signal: In sigqueueinfo prefer sig not si_signo
From: Eric W. Biederman <hidden>
Date: 2018-10-05 07:11:02
Also in:
linux-arch, lkml
Subsystem:
the rest · Maintainer:
Linus Torvalds
Andrei Vagin [off-list ref] reported:
Accoding to the man page, the user should not set si_signo, it has to be set by kernel. $ man 2 rt_sigqueueinfo The uinfo argument specifies the data to accompany the signal. This argument is a pointer to a structure of type siginfo_t, described in sigaction(2) (and defined by including <sigaction.h>). The caller should set the following fields in this structure: si_code This must be one of the SI_* codes in the Linux kernel source file include/asm-generic/siginfo.h, with the restriction that the code must be negative (i.e., cannot be SI_USER, which is used by the kernel to indicate a signal sent by kill(2)) and cannot (since Linux 2.6.39) be SI_TKILL (which is used by the kernel to indicate a signal sent using tgkill(2)). si_pid This should be set to a process ID, typically the process ID of the sender. si_uid This should be set to a user ID, typically the real user ID of the sender. si_value This field contains the user data to accompany the signal. For more information, see the description of the last (union sigval) argument of sigqueue(3). Internally, the kernel sets the si_signo field to the value specified in sig, so that the receiver of the signal can also obtain the signal number via that field. On Tue, Sep 25, 2018 at 07:19:02PM +0200, Eric W. Biederman wrote:quoted
If there is some application that calls sigqueueinfo directly that has a problem with this added sanity check we can revisit this when we see what kind of crazy that application is doing.I already know two "applications" ;) https://github.com/torvalds/linux/blob/master/tools/testing/selftests/ptrace/peeksiginfo.c https://github.com/checkpoint-restore/criu/blob/master/test/zdtm/static/sigpending.c Disclaimer: I'm the author of both of them.
Looking at the kernel code the historical behavior has alwasy been to prefer
the signal number passed in by the kernel.
So sigh. Implmenet __copy_siginfo_from_user and __copy_siginfo_from_user32 to
take that signal number and prefer it. The user of ptrace will still
use copy_siginfo_from_user and copy_siginfo_from_user32 as they do not and
never have had a signal number there.
Luckily this change has never made it farther than linux-next.
Fixes: e75dc036c445 ("signal: Fail sigqueueinfo if si_signo != sig")
Signed-off-by: "Eric W. Biederman" <redacted>
---
Andrei can you verify this fixes your programs?
Thank you very much,
Eric
kernel/signal.c | 141 ++++++++++++++++++++++++++++--------------------
1 file changed, 84 insertions(+), 57 deletions(-)
diff --git a/kernel/signal.c b/kernel/signal.c
index 1c2dd117fee0..2bffc5a50183 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c@@ -2925,11 +2925,10 @@ int copy_siginfo_to_user(siginfo_t __user *to, const kernel_siginfo_t *from) return 0; } -int copy_siginfo_from_user(kernel_siginfo_t *to, const siginfo_t __user *from) +static int post_copy_siginfo_from_user(kernel_siginfo_t *info, + const siginfo_t __user *from) { - if (copy_from_user(to, from, sizeof(struct kernel_siginfo))) - return -EFAULT; - if (unlikely(!known_siginfo_layout(to->si_signo, to->si_code))) { + if (unlikely(!known_siginfo_layout(info->si_signo, info->si_code))) { char __user *expansion = si_expansion(from); char buf[SI_EXPANSION_SIZE]; int i;
@@ -2949,6 +2948,22 @@ int copy_siginfo_from_user(kernel_siginfo_t *to, const siginfo_t __user *from) return 0; } +static int __copy_siginfo_from_user(int signo, kernel_siginfo_t *to, + const siginfo_t __user *from) +{ + if (copy_from_user(to, from, sizeof(struct kernel_siginfo))) + return -EFAULT; + to->si_signo = signo; + return post_copy_siginfo_from_user(to, from); +} + +int copy_siginfo_from_user(kernel_siginfo_t *to, const siginfo_t __user *from) +{ + if (copy_from_user(to, from, sizeof(struct kernel_siginfo))) + return -EFAULT; + return post_copy_siginfo_from_user(to, from); +} + #ifdef CONFIG_COMPAT int copy_siginfo_to_user32(struct compat_siginfo __user *to, const struct kernel_siginfo *from)
@@ -3041,88 +3056,106 @@ int __copy_siginfo_to_user32(struct compat_siginfo __user *to, return 0; } -int copy_siginfo_from_user32(struct kernel_siginfo *to, - const struct compat_siginfo __user *ufrom) +static int post_copy_siginfo_from_user32(kernel_siginfo_t *to, + const struct compat_siginfo *from) { - struct compat_siginfo from; - - if (copy_from_user(&from, ufrom, sizeof(struct compat_siginfo))) - return -EFAULT; - clear_siginfo(to); - to->si_signo = from.si_signo; - to->si_errno = from.si_errno; - to->si_code = from.si_code; - switch(siginfo_layout(from.si_signo, from.si_code)) { + to->si_signo = from->si_signo; + to->si_errno = from->si_errno; + to->si_code = from->si_code; + switch(siginfo_layout(from->si_signo, from->si_code)) { case SIL_KILL: - to->si_pid = from.si_pid; - to->si_uid = from.si_uid; + to->si_pid = from->si_pid; + to->si_uid = from->si_uid; break; case SIL_TIMER: - to->si_tid = from.si_tid; - to->si_overrun = from.si_overrun; - to->si_int = from.si_int; + to->si_tid = from->si_tid; + to->si_overrun = from->si_overrun; + to->si_int = from->si_int; break; case SIL_POLL: - to->si_band = from.si_band; - to->si_fd = from.si_fd; + to->si_band = from->si_band; + to->si_fd = from->si_fd; break; case SIL_FAULT: - to->si_addr = compat_ptr(from.si_addr); + to->si_addr = compat_ptr(from->si_addr); #ifdef __ARCH_SI_TRAPNO - to->si_trapno = from.si_trapno; + to->si_trapno = from->si_trapno; #endif break; case SIL_FAULT_MCEERR: - to->si_addr = compat_ptr(from.si_addr); + to->si_addr = compat_ptr(from->si_addr); #ifdef __ARCH_SI_TRAPNO - to->si_trapno = from.si_trapno; + to->si_trapno = from->si_trapno; #endif - to->si_addr_lsb = from.si_addr_lsb; + to->si_addr_lsb = from->si_addr_lsb; break; case SIL_FAULT_BNDERR: - to->si_addr = compat_ptr(from.si_addr); + to->si_addr = compat_ptr(from->si_addr); #ifdef __ARCH_SI_TRAPNO - to->si_trapno = from.si_trapno; + to->si_trapno = from->si_trapno; #endif - to->si_lower = compat_ptr(from.si_lower); - to->si_upper = compat_ptr(from.si_upper); + to->si_lower = compat_ptr(from->si_lower); + to->si_upper = compat_ptr(from->si_upper); break; case SIL_FAULT_PKUERR: - to->si_addr = compat_ptr(from.si_addr); + to->si_addr = compat_ptr(from->si_addr); #ifdef __ARCH_SI_TRAPNO - to->si_trapno = from.si_trapno; + to->si_trapno = from->si_trapno; #endif - to->si_pkey = from.si_pkey; + to->si_pkey = from->si_pkey; break; case SIL_CHLD: - to->si_pid = from.si_pid; - to->si_uid = from.si_uid; - to->si_status = from.si_status; + to->si_pid = from->si_pid; + to->si_uid = from->si_uid; + to->si_status = from->si_status; #ifdef CONFIG_X86_X32_ABI if (in_x32_syscall()) { - to->si_utime = from._sifields._sigchld_x32._utime; - to->si_stime = from._sifields._sigchld_x32._stime; + to->si_utime = from->_sifields._sigchld_x32._utime; + to->si_stime = from->_sifields._sigchld_x32._stime; } else #endif { - to->si_utime = from.si_utime; - to->si_stime = from.si_stime; + to->si_utime = from->si_utime; + to->si_stime = from->si_stime; } break; case SIL_RT: - to->si_pid = from.si_pid; - to->si_uid = from.si_uid; - to->si_int = from.si_int; + to->si_pid = from->si_pid; + to->si_uid = from->si_uid; + to->si_int = from->si_int; break; case SIL_SYS: - to->si_call_addr = compat_ptr(from.si_call_addr); - to->si_syscall = from.si_syscall; - to->si_arch = from.si_arch; + to->si_call_addr = compat_ptr(from->si_call_addr); + to->si_syscall = from->si_syscall; + to->si_arch = from->si_arch; break; } return 0; } + +static int __copy_siginfo_from_user32(int signo, struct kernel_siginfo *to, + const struct compat_siginfo __user *ufrom) +{ + struct compat_siginfo from; + + if (copy_from_user(&from, ufrom, sizeof(struct compat_siginfo))) + return -EFAULT; + + from.si_signo = signo; + return post_copy_siginfo_from_user32(to, &from); +} + +int copy_siginfo_from_user32(struct kernel_siginfo *to, + const struct compat_siginfo __user *ufrom) +{ + struct compat_siginfo from; + + if (copy_from_user(&from, ufrom, sizeof(struct compat_siginfo))) + return -EFAULT; + + return post_copy_siginfo_from_user32(to, &from); +} #endif /* CONFIG_COMPAT */ /**
@@ -3359,9 +3392,6 @@ static int do_rt_sigqueueinfo(pid_t pid, int sig, kernel_siginfo_t *info) (task_pid_vnr(current) != pid)) return -EPERM; - if (info->si_signo != sig) - return -EINVAL; - /* POSIX.1b doesn't mention process groups. */ return kill_proc_info(sig, info, pid); }
@@ -3376,7 +3406,7 @@ SYSCALL_DEFINE3(rt_sigqueueinfo, pid_t, pid, int, sig, siginfo_t __user *, uinfo) { kernel_siginfo_t info; - int ret = copy_siginfo_from_user(&info, uinfo); + int ret = __copy_siginfo_from_user(sig, &info, uinfo); if (unlikely(ret)) return ret; return do_rt_sigqueueinfo(pid, sig, &info);
@@ -3389,7 +3419,7 @@ COMPAT_SYSCALL_DEFINE3(rt_sigqueueinfo, struct compat_siginfo __user *, uinfo) { kernel_siginfo_t info; - int ret = copy_siginfo_from_user32(&info, uinfo); + int ret = __copy_siginfo_from_user32(sig, &info, uinfo); if (unlikely(ret)) return ret; return do_rt_sigqueueinfo(pid, sig, &info);
@@ -3409,9 +3439,6 @@ static int do_rt_tgsigqueueinfo(pid_t tgid, pid_t pid, int sig, kernel_siginfo_t (task_pid_vnr(current) != pid)) return -EPERM; - if (info->si_signo != sig) - return -EINVAL; - return do_send_specific(tgid, pid, sig, info); }
@@ -3419,7 +3446,7 @@ SYSCALL_DEFINE4(rt_tgsigqueueinfo, pid_t, tgid, pid_t, pid, int, sig, siginfo_t __user *, uinfo) { kernel_siginfo_t info; - int ret = copy_siginfo_from_user(&info, uinfo); + int ret = __copy_siginfo_from_user(sig, &info, uinfo); if (unlikely(ret)) return ret; return do_rt_tgsigqueueinfo(tgid, pid, sig, &info);
@@ -3433,7 +3460,7 @@ COMPAT_SYSCALL_DEFINE4(rt_tgsigqueueinfo, struct compat_siginfo __user *, uinfo) { kernel_siginfo_t info; - int ret = copy_siginfo_from_user32(&info, uinfo); + int ret = __copy_siginfo_from_user32(sig, &info, uinfo); if (unlikely(ret)) return ret; return do_rt_tgsigqueueinfo(tgid, pid, sig, &info);