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authorDmitry V. Levin <ldv@altlinux.org>2020-06-02 21:00:51 +0300
committerVasily Gorbik <gor@linux.ibm.com>2020-06-17 23:05:05 +0200
commitb3583fca5fb654af2cfc1c08259abb9728272538 (patch)
treeef9096a292898761281983a0755af0e06ad75349 /arch/s390/include/asm
parentc920c545286270302d29fd63c05c3bd84828daee (diff)
downloadlinux-sh-b3583fca5fb654af2cfc1c08259abb9728272538.tar.gz
s390: fix syscall_get_error for compat processes
If both the tracer and the tracee are compat processes, and gprs[2] is assigned a value by __poke_user_compat, then the higher 32 bits of gprs[2] are cleared, IS_ERR_VALUE() always returns false, and syscall_get_error() always returns 0. Fix the implementation by sign-extending the value for compat processes the same way as x86 implementation does. The bug was exposed to user space by commit 201766a20e30f ("ptrace: add PTRACE_GET_SYSCALL_INFO request") and detected by strace test suite. This change fixes strace syscall tampering on s390. Link: https://lkml.kernel.org/r/20200602180051.GA2427@altlinux.org Fixes: 753c4dd6a2fa2 ("[S390] ptrace changes") Cc: Elvira Khabirova <lineprinter@altlinux.org> Cc: stable@vger.kernel.org # v2.6.28+ Signed-off-by: Dmitry V. Levin <ldv@altlinux.org> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Diffstat (limited to 'arch/s390/include/asm')
-rw-r--r--arch/s390/include/asm/syscall.h12
1 files changed, 11 insertions, 1 deletions
diff --git a/arch/s390/include/asm/syscall.h b/arch/s390/include/asm/syscall.h
index f073292e9fdb..d9d5de0f67ff 100644
--- a/arch/s390/include/asm/syscall.h
+++ b/arch/s390/include/asm/syscall.h
@@ -33,7 +33,17 @@ static inline void syscall_rollback(struct task_struct *task,
static inline long syscall_get_error(struct task_struct *task,
struct pt_regs *regs)
{
- return IS_ERR_VALUE(regs->gprs[2]) ? regs->gprs[2] : 0;
+ unsigned long error = regs->gprs[2];
+#ifdef CONFIG_COMPAT
+ if (test_tsk_thread_flag(task, TIF_31BIT)) {
+ /*
+ * Sign-extend the value so (int)-EFOO becomes (long)-EFOO
+ * and will match correctly in comparisons.
+ */
+ error = (long)(int)error;
+ }
+#endif
+ return IS_ERR_VALUE(error) ? error : 0;
}
static inline long syscall_get_return_value(struct task_struct *task,