We have hit an issue where our 32-bit applications using poll() and
passing in a value of -1 for the timeout value return after ~49 days
(2^32 msec), instead of waiting indefinitely. I've instrumented the
kernel and found we are hitting the case where poll() believes we've
passed in a positive number and thus creates a timespec, etc. I've
implemented compat_sys_poll() to sign-extend the timeout value and
resolve the issue.
There was an almost identical patch submitted last year, but for
whatever reason did not make it in:
https://lkml.org/lkml/2011/9/18/19
I am guessing there are other architectures affected by this bug. This
patch only fixes x86.
Josh
commit cde9eb901ccb3b5af3e501b018b90f16c53942c2
Author: Josh Hunt <johunt@xxxxxxxxxx>
Date: Mon Feb 6 20:51:31 2012 -0800
compat: poll() in 32-bit applications does not handle negative timeout values properly on 64-bit kernels
We have observed our 32-bit applications running on 64-bit kernels do not
wait infinitely when passed a negative value for the timeout argument.
Instead we see poll() returning in ~49 days or 2^32 msecs, because the
timeout argument is not getting sign-extended. Implementing
compat_sys_poll() to handle this case.
Reported-by: Phil Lisiecki <lisiecki@xxxxxxxxxx>
Signed-off-by: Josh Hunt <johunt@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
diff --git a/arch/x86/syscalls/syscall_32.tbl b/arch/x86/syscalls/syscall_32.tbl
index ce98e28..8407150 100644
--- a/arch/x86/syscalls/syscall_32.tbl
+++ b/arch/x86/syscalls/syscall_32.tbl
@@ -174,7 +174,7 @@
165 i386 getresuid sys_getresuid16
166 i386 vm86 ptregs_vm86 sys32_vm86_warning
167 i386 query_module
-168 i386 poll sys_poll
+168 i386 poll sys_poll compat_sys_poll
169 i386 nfsservctl
170 i386 setresgid sys_setresgid16
171 i386 getresgid sys_getresgid16
diff --git a/fs/compat.c b/fs/compat.c
index fa9d721..77bd50e 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -1611,6 +1611,12 @@ asmlinkage long compat_sys_pselect6(int n, compat_ulong_t __user *inp,
sigsetsize);
}
+asmlinkage long compat_sys_poll(struct pollfd __user *ufds, unsigned int nfds,
+ int timeout_msecs)
+{
+ return sys_poll(ufds, nfds, timeout_msecs);
+}
+
asmlinkage long compat_sys_ppoll(struct pollfd __user *ufds,
unsigned int nfds, struct compat_timespec __user *tsp,
const compat_sigset_t __user *sigmask, compat_size_t sigsetsize)
diff --git a/include/linux/compat.h b/include/linux/compat.h
index 41c9f65..66e61e0 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -433,6 +433,8 @@ asmlinkage long compat_sys_pselect6(int n, compat_ulong_t __user *inp,
compat_ulong_t __user *exp,
struct compat_timespec __user *tsp,
void __user *sig);
+asmlinkage long compat_sys_poll(struct pollfd __user *ufds, unsigned int nfds,
+ int timeout_msecs);
asmlinkage long compat_sys_ppoll(struct pollfd __user *ufds,
unsigned int nfds,
struct compat_timespec __user *tsp,
