Mitigation for "clone on sparc might fail with -EFAULT for no valid reason" (bz 31394)

It seems the kernel can not deal with uncommitted stack space in the area intended
for the register window when executing the clone() system call. So create a nested
frame (proxy for the kernel frame) and flush it from the processor to memory to
force committing pages to the stack before invoking the system call.

Bug: https://www.mail-archive.com/debian-glibc@lists.debian.org/msg62592.html
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31394
See-also: https://lore.kernel.org/sparclinux/62f9be9d-a086-4134-9a9f-5df8822708af@mkarcher.dialup.fu-berlin.de/
Signed-off-by: Michael Karcher <sourceware-bugzilla@mkarcher.dialup.fu-berlin.de>
Reviewed-by: DJ Delorie <dj@redhat.com>
(cherry picked from commit faeaa3bc9f76030b9882ccfdee232fc0ca6dcb06)

diff --git a/NEWS b/NEWS
index 928c516bec8ee983d57e0b3522a6a833c9c43bc2..dc815fb6d37a14db1fb43754cef0900367a3cabc 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -11,6 +11,7 @@ The following bugs are resolved with this release:
 
   [27821] ungetc: Fix backup buffer leak on program exit
   [30081] resolv: Do not wait for non-existing second DNS response after error
+  [31394] clone on sparc might fail with -EFAULT for no valid reason
   [31717] elf: Avoid re-initializing already allocated TLS in dlopen
   [31890] resolv: Allow short error responses to match any DNS query
   [31968] mremap implementation in C does not handle arguments correctly

diff --git a/sysdeps/unix/sysv/linux/sparc/sparc32/clone.S b/sysdeps/unix/sysv/linux/sparc/sparc32/clone.S
index 748d25fcfed597dc8ae671dcbbe81976976484b3..c9cf9bb055bc0c5cba57d14cbe27d44877e28dd3 100644 (file)
--- a/sysdeps/unix/sysv/linux/sparc/sparc32/clone.S
+++ b/sysdeps/unix/sysv/linux/sparc/sparc32/clone.S
@@ -28,6 +28,9 @@
        .text
 ENTRY (__clone)
        save    %sp,-96,%sp
+       save    %sp,-96,%sp
+       flushw
+       restore
        cfi_def_cfa_register(%fp)
        cfi_window_save
        cfi_register(%o7, %i7)

diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/clone.S b/sysdeps/unix/sysv/linux/sparc/sparc64/clone.S
index e5ff2cf1a042aeae95514823b2793366512adbea..370d51fda295232efaa985b244059b8adab060fb 100644 (file)
--- a/sysdeps/unix/sysv/linux/sparc/sparc64/clone.S
+++ b/sysdeps/unix/sysv/linux/sparc/sparc64/clone.S
@@ -32,6 +32,9 @@
 
 ENTRY (__clone)
        save    %sp, -192, %sp
+       save    %sp, -192, %sp
+       flushw
+       restore
        cfi_def_cfa_register(%fp)
        cfi_window_save
        cfi_register(%o7, %i7)