From: Jeff Dike Date: Thu, 1 Mar 2007 04:13:06 +0000 (-0800) Subject: [PATCH] uml: fix host LDT lookup initialization locking, try 2 X-Git-Tag: v2.6.21-rc3~170 X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=af727902212343211627da14d17c85592feb0e18;p=linux-2.6-omap-h63xx.git [PATCH] uml: fix host LDT lookup initialization locking, try 2 Add some locking to host_ldt_entries to prevent racing when reading LDT information from the host. The locking is somewhat more careful than my previous attempt. Now, only the check of host_ldt_entries is locked. The lock is dropped immediately afterwards, and if the LDT needs initializing, that (and the memory allocations needed) proceed outside the lock. Also fixed some style violations. Signed-off-by: Jeff Dike Cc: Paolo 'Blaisorblade' Giarrusso Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/arch/um/sys-i386/ldt.c b/arch/um/sys-i386/ldt.c index 5db7737df0f..4a8b4202ef9 100644 --- a/arch/um/sys-i386/ldt.c +++ b/arch/um/sys-i386/ldt.c @@ -7,6 +7,7 @@ #include "linux/slab.h" #include "linux/types.h" #include "linux/errno.h" +#include "linux/spinlock.h" #include "asm/uaccess.h" #include "asm/smp.h" #include "asm/ldt.h" @@ -386,23 +387,33 @@ static long do_modify_ldt_skas(int func, void __user *ptr, return ret; } -short dummy_list[9] = {0, -1}; -short * host_ldt_entries = NULL; +static DEFINE_SPINLOCK(host_ldt_lock); +static short dummy_list[9] = {0, -1}; +static short * host_ldt_entries = NULL; -void ldt_get_host_info(void) +static void ldt_get_host_info(void) { long ret; - struct ldt_entry * ldt; + struct ldt_entry * ldt, *tmp; int i, size, k, order; + spin_lock(&host_ldt_lock); + + if(host_ldt_entries != NULL){ + spin_unlock(&host_ldt_lock); + return; + } host_ldt_entries = dummy_list+1; + spin_unlock(&host_ldt_lock); + for(i = LDT_PAGES_MAX-1, order=0; i; i>>=1, order++); ldt = (struct ldt_entry *) __get_free_pages(GFP_KERNEL|__GFP_ZERO, order); if(ldt == NULL) { - printk("ldt_get_host_info: couldn't allocate buffer for host ldt\n"); + printk("ldt_get_host_info: couldn't allocate buffer for host " + "ldt\n"); return; } @@ -426,11 +437,13 @@ void ldt_get_host_info(void) host_ldt_entries = dummy_list; else { size = (size + 1) * sizeof(dummy_list[0]); - host_ldt_entries = kmalloc(size, GFP_KERNEL); - if(host_ldt_entries == NULL) { - printk("ldt_get_host_info: couldn't allocate host ldt list\n"); + tmp = kmalloc(size, GFP_KERNEL); + if(tmp == NULL) { + printk("ldt_get_host_info: couldn't allocate host ldt " + "list\n"); goto out_free; } + host_ldt_entries = tmp; } for(i=0, k=0; iid, 1, &desc, @@ -560,6 +572,6 @@ void free_ldt(struct mmu_context_skas * mm) int sys_modify_ldt(int func, void __user *ptr, unsigned long bytecount) { - return(CHOOSE_MODE_PROC(do_modify_ldt_tt, do_modify_ldt_skas, func, - ptr, bytecount)); + return CHOOSE_MODE_PROC(do_modify_ldt_tt, do_modify_ldt_skas, func, + ptr, bytecount); }