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ARM: fix a cockup in 48be69a02 (ARM: move signal handlers into a vdso-like page)

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Unfortunately, I never committed the fix to a nasty oops which can
occur as a result of that commit:

------------[ cut here ]------------
kernel BUG at /home/olof/work/batch/include/linux/mm.h:414!
Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
Modules linked in:
CPU: 0 PID: 490 Comm: killall5 Not tainted 3.11.0-rc3-00288-gabe0308 #53
task: e90acac0 ti: e9be8000 task.ti: e9be8000
PC is at special_mapping_fault+0xa4/0xc4
LR is at __do_fault+0x68/0x48c

This doesn't show up unless you do quite a bit of testing; a simple
boot test does not do this, so all my nightly tests were passing fine.

The reason for this is that install_special_mapping() expects the
page array to stick around, and as this was only inserting one page
which was stored on the kernel stack, that's why this was blowing up.

Reported-by: Olof Johansson <olof@lixom.net>
Tested-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Russell King 2013-08-03 10:30:05 +01:00
parent a5463cd343
commit e0d407564b
2 changed files with 24 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
arch/arm/kernel/process.c
View File

@ -471,17 +471,18 @@ const char *arch_vma_name(struct vm_area_struct *vma)
"[sigpage]" : NULL; "[sigpage]" : NULL;
} }
static struct page *signal_page;
extern struct page *get_signal_page(void); extern struct page *get_signal_page(void);
int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
{ {
struct mm_struct *mm = current->mm; struct mm_struct *mm = current->mm;
struct page *page;
unsigned long addr; unsigned long addr;
int ret; int ret;
page = get_signal_page(); if (!signal_page)
if (!page) signal_page = get_signal_page();
if (!signal_page)
return -ENOMEM; return -ENOMEM;
down_write(&mm->mmap_sem); down_write(&mm->mmap_sem);
@ -493,7 +494,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
ret = install_special_mapping(mm, addr, PAGE_SIZE, ret = install_special_mapping(mm, addr, PAGE_SIZE,
VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC, VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
&page); &signal_page);
if (ret == 0) if (ret == 0)
mm->context.sigpage = addr; mm->context.sigpage = addr;

41
arch/arm/kernel/signal.c
View File

@ -614,35 +614,32 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
return 0; return 0;
} }
static struct page *signal_page;
struct page *get_signal_page(void) struct page *get_signal_page(void)
{ {
if (!signal_page) { unsigned long ptr;
unsigned long ptr; unsigned offset;
unsigned offset; struct page *page;
void *addr; void *addr;
signal_page = alloc_pages(GFP_KERNEL, 0); page = alloc_pages(GFP_KERNEL, 0);
if (!signal_page) if (!page)
return NULL; return NULL;
addr = page_address(signal_page); addr = page_address(page);
/* Give the signal return code some randomness */ /* Give the signal return code some randomness */
offset = 0x200 + (get_random_int() & 0x7fc); offset = 0x200 + (get_random_int() & 0x7fc);
signal_return_offset = offset; signal_return_offset = offset;
/* /*
* Copy signal return handlers into the vector page, and * Copy signal return handlers into the vector page, and
* set sigreturn to be a pointer to these. * set sigreturn to be a pointer to these.
*/ */
memcpy(addr + offset, sigreturn_codes, sizeof(sigreturn_codes)); memcpy(addr + offset, sigreturn_codes, sizeof(sigreturn_codes));
ptr = (unsigned long)addr + offset; ptr = (unsigned long)addr + offset;
flush_icache_range(ptr, ptr + sizeof(sigreturn_codes)); flush_icache_range(ptr, ptr + sizeof(sigreturn_codes));
}
return signal_page; return page;
} }