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head/emulators/xen-kernel47/files/xsa249.patch
| Property | Old Value | New Value |
|---|---|---|
| fbsd:nokeywords | null | yes \ No newline at end of property |
| svn:eol-style | null | native \ No newline at end of property |
| svn:mime-type | null | text/plain \ No newline at end of property |
| From: Jan Beulich <jbeulich@suse.com> | |||||
| Subject: x86/shadow: fix refcount overflow check | |||||
| Commit c385d27079 ("x86 shadow: for multi-page shadows, explicitly track | |||||
| the first page") reduced the refcount width to 25, without adjusting the | |||||
| overflow check. Eliminate the disconnect by using a manifest constant. | |||||
| Interestingly, up to commit 047782fa01 ("Out-of-sync L1 shadows: OOS | |||||
| snapshot") the refcount was 27 bits wide, yet the check was already | |||||
| using 26. | |||||
| This is XSA-249. | |||||
| Signed-off-by: Jan Beulich <jbeulich@suse.com> | |||||
| Reviewed-by: George Dunlap <george.dunlap@citrix.com> | |||||
| Reviewed-by: Tim Deegan <tim@xen.org> | |||||
| --- | |||||
| v2: Simplify expression back to the style it was. | |||||
| --- a/xen/arch/x86/mm/shadow/private.h | |||||
| +++ b/xen/arch/x86/mm/shadow/private.h | |||||
| @@ -529,7 +529,7 @@ static inline int sh_get_ref(struct doma | |||||
| x = sp->u.sh.count; | |||||
| nx = x + 1; | |||||
| - if ( unlikely(nx >= 1U<<26) ) | |||||
| + if ( unlikely(nx >= (1U << PAGE_SH_REFCOUNT_WIDTH)) ) | |||||
| { | |||||
| SHADOW_PRINTK("shadow ref overflow, gmfn=%lx smfn=%lx\n", | |||||
| __backpointer(sp), mfn_x(smfn)); | |||||
| --- a/xen/include/asm-x86/mm.h | |||||
| +++ b/xen/include/asm-x86/mm.h | |||||
| @@ -82,7 +82,8 @@ struct page_info | |||||
| unsigned long type:5; /* What kind of shadow is this? */ | |||||
| unsigned long pinned:1; /* Is the shadow pinned? */ | |||||
| unsigned long head:1; /* Is this the first page of the shadow? */ | |||||
| - unsigned long count:25; /* Reference count */ | |||||
| +#define PAGE_SH_REFCOUNT_WIDTH 25 | |||||
| + unsigned long count:PAGE_SH_REFCOUNT_WIDTH; /* Reference count */ | |||||
| } sh; | |||||
| /* Page is on a free list: ((count_info & PGC_count_mask) == 0). */ | |||||