After getting a report of 3.2.3's xenmon crashing Xen (as it turned out
this was because c/s 17000 was backported to that tree without also
applying c/s 17515), this is the result of reviewing the code for
security issues:
- the hypervisor should not rely on any specific state of the actual
trace buffer (as it is shared writable with Dom0)
- there's no need to share writably the t_info pages (Dom0 only wants
[and needs] to read it)
- T_INFO_FIRST_OFFSET wasn't defined correctly, thus allowing in the
num_online_cpus() == NR_CPUS case to pass a corrupted MFN to Dom0
- check_tbuf_size() didn't consider the case of the incoming size not
allowing for the 2*data_size range for t_buf->{prod,cons}
- printk()-s should be lower level or rate limited
For the first of those items, I chose to use 'volatile' qualifiers
rather than sprinkling around barriers - this can certainly be changed
if considered unacceptable.
To make clear what purpose specific variables have and/or where they
got loaded from, the patch also changes the type of some of them to
be explicitly u32/s32, and removes pointless assertions (like checking
an unsigned variable to be >= 0).
I also took the prototype adjustment of __trace_var() as an opportunity
to simplify the TRACE_xD() macros. Similar simplification could be done
on the (quite numerous) direct callers of the function.
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
--- 2010-06-15.orig/tools/xenmon/xenbaked.c 2010-06-01 13:39:57.000000000
+0200
+++ 2010-06-15/tools/xenmon/xenbaked.c 2010-06-28 10:23:01.000000000 +0200
@@ -84,7 +84,7 @@ typedef struct settings_st {
} settings_t;
struct t_struct {
- struct t_info *t_info; /* Structure with information about individual
buffers */
+ const struct t_info *t_info; /* Structure with information about
individual buffers */
struct t_buf **meta; /* Pointers to trace buffer metadata */
unsigned char **data; /* Pointers to trace buffer data areas */
};
@@ -376,9 +376,8 @@ static struct t_struct *map_tbufs(unsign
}
/* Map t_info metadata structure */
- tbufs.t_info = xc_map_foreign_range(xc_handle, DOMID_XEN,
- tinfo_size, PROT_READ | PROT_WRITE,
- tbufs_mfn);
+ tbufs.t_info = xc_map_foreign_range(xc_handle, DOMID_XEN, tinfo_size,
+ PROT_READ, tbufs_mfn);
if ( tbufs.t_info == 0 )
{
@@ -404,7 +403,8 @@ static struct t_struct *map_tbufs(unsign
for(i=0; i<num; i++)
{
- uint32_t *mfn_list = ((uint32_t *)tbufs.t_info) +
tbufs.t_info->mfn_offset[i];
+ const uint32_t *mfn_list = (const uint32_t *)tbufs.t_info
+ + tbufs.t_info->mfn_offset[i];
int j;
xen_pfn_t pfn_list[tbufs.t_info->tbuf_size];
--- 2010-06-15.orig/tools/xentrace/xentrace.c 2010-06-01 13:39:57.000000000
+0200
+++ 2010-06-15/tools/xentrace/xentrace.c 2010-06-28 10:23:26.000000000
+0200
@@ -63,7 +63,7 @@ typedef struct settings_st {
} settings_t;
struct t_struct {
- struct t_info *t_info; /* Structure with information about individual
buffers */
+ const struct t_info *t_info; /* Structure with information about
individual buffers */
struct t_buf **meta; /* Pointers to trace buffer metadata */
unsigned char **data; /* Pointers to trace buffer data areas */
};
@@ -475,9 +475,8 @@ static struct t_struct *map_tbufs(unsign
int i;
/* Map t_info metadata structure */
- tbufs.t_info = xc_map_foreign_range(xc_handle, DOMID_XEN,
- tinfo_size, PROT_READ | PROT_WRITE,
- tbufs_mfn);
+ tbufs.t_info = xc_map_foreign_range(xc_handle, DOMID_XEN, tinfo_size,
+ PROT_READ, tbufs_mfn);
if ( tbufs.t_info == 0 )
{
@@ -503,7 +502,8 @@ static struct t_struct *map_tbufs(unsign
for(i=0; i<num; i++)
{
- uint32_t *mfn_list = ((uint32_t *)tbufs.t_info) +
tbufs.t_info->mfn_offset[i];
+ const uint32_t *mfn_list = (const uint32_t *)tbufs.t_info
+ + tbufs.t_info->mfn_offset[i];
int j;
xen_pfn_t pfn_list[tbufs.t_info->tbuf_size];
--- 2010-06-15.orig/xen/common/trace.c 2010-06-28 09:43:58.000000000 +0200
+++ 2010-06-15/xen/common/trace.c 2010-06-28 11:58:37.000000000 +0200
@@ -51,15 +51,15 @@ static struct t_info *t_info;
#define T_INFO_PAGES 2 /* Size fixed at 2 pages for now. */
#define T_INFO_SIZE ((T_INFO_PAGES)*(PAGE_SIZE))
/* t_info.tbuf_size + list of mfn offsets + 1 to round up / sizeof uint32_t */
-#define T_INFO_FIRST_OFFSET ((sizeof(int16_t) + NR_CPUS * sizeof(int16_t) + 1)
/ sizeof(uint32_t))
-static DEFINE_PER_CPU_READ_MOSTLY(struct t_buf *, t_bufs);
+#define T_INFO_FIRST_OFFSET (((2 + NR_CPUS) * sizeof(uint16_t)) /
sizeof(uint32_t))
+static DEFINE_PER_CPU_READ_MOSTLY(volatile struct t_buf *, t_bufs);
static DEFINE_PER_CPU_READ_MOSTLY(unsigned char *, t_data);
static DEFINE_PER_CPU_READ_MOSTLY(spinlock_t, t_lock);
-static int data_size;
+static u32 data_size;
/* High water mark for trace buffers; */
/* Send virtual interrupt when buffer level reaches this point */
-static int t_buf_highwater;
+static u32 t_buf_highwater;
/* Number of records lost due to per-CPU trace buffer being full. */
static DEFINE_PER_CPU(unsigned long, lost_records);
@@ -77,11 +77,16 @@ static u32 tb_event_mask = TRC_ALL;
/**
* check_tbuf_size - check to make sure that the proposed size will fit
- * in the currently sized struct t_info.
+ * in the currently sized struct t_info and allows prod and cons to
+ * reach double the value without overflow.
*/
-static inline int check_tbuf_size(int size)
+static int check_tbuf_size(u32 pages)
{
- return (num_online_cpus() * size + T_INFO_FIRST_OFFSET) > (T_INFO_SIZE /
sizeof(uint32_t));
+ u32 size = pages * PAGE_SIZE;
+
+ return (size / PAGE_SIZE != pages) || (size + size < size) ||
+ (num_online_cpus() * pages + T_INFO_FIRST_OFFSET >
+ T_INFO_SIZE / sizeof(uint32_t));
}
/**
@@ -115,7 +120,7 @@ static int alloc_trace_bufs(void)
}
t_info->tbuf_size = opt_tbuf_size;
- printk("tbuf_size %d\n", t_info->tbuf_size);
+ printk(XENLOG_INFO "tbuf_size %d\n", t_info->tbuf_size);
nr_pages = opt_tbuf_size;
order = get_order_from_pages(nr_pages);
@@ -139,7 +144,7 @@ static int alloc_trace_bufs(void)
spin_lock_irqsave(&per_cpu(t_lock, cpu), flags);
- buf = per_cpu(t_bufs, cpu) = (struct t_buf *)rawbuf;
+ per_cpu(t_bufs, cpu) = buf = (struct t_buf *)rawbuf;
buf->cons = buf->prod = 0;
per_cpu(t_data, cpu) = (unsigned char *)(buf + 1);
@@ -171,7 +176,7 @@ static int alloc_trace_bufs(void)
/* Write list first, then write per-cpu offset. */
wmb();
t_info->mfn_offset[cpu]=offset;
- printk("p%d mfn %"PRIx32" offset %d\n",
+ printk(XENLOG_INFO "p%d mfn %"PRIx32" offset %d\n",
cpu, mfn, offset);
offset+=i;
}
@@ -190,6 +195,7 @@ out_dealloc:
spin_lock_irqsave(&per_cpu(t_lock, cpu), flags);
if ( (rawbuf = (char *)per_cpu(t_bufs, cpu)) )
{
+ per_cpu(t_bufs, cpu) = NULL;
ASSERT(!(virt_to_page(rawbuf)->count_info & PGC_allocated));
free_xenheap_pages(rawbuf, order);
}
@@ -308,7 +314,7 @@ void __init init_trace_bufs(void)
for(i=0; i<T_INFO_PAGES; i++)
share_xen_page_with_privileged_guests(
- virt_to_page(t_info) + i, XENSHARE_writable);
+ virt_to_page(t_info) + i, XENSHARE_readonly);
if ( opt_tbuf_size == 0 )
{
@@ -404,19 +410,37 @@ int tb_control(xen_sysctl_tbuf_op_t *tbc
return rc;
}
-static inline int calc_rec_size(int cycles, int extra)
+static inline unsigned int calc_rec_size(bool_t cycles, unsigned int extra)
{
- int rec_size;
- rec_size = 4;
+ unsigned int rec_size = 4;
+
if ( cycles )
rec_size += 8;
rec_size += extra;
return rec_size;
}
-static inline int calc_unconsumed_bytes(struct t_buf *buf)
+static inline bool_t bogus(u32 prod, u32 cons)
+{
+ if ( unlikely(prod & 3) || unlikely(prod >= 2 * data_size) ||
+ unlikely(cons & 3) || unlikely(cons >= 2 * data_size) )
+ {
+ tb_init_done = 0;
+ printk(XENLOG_WARNING "trc#%u: bogus prod (%08x) and/or cons (%08x)\n",
+ smp_processor_id(), prod, cons);
+ return 1;
+ }
+ return 0;
+}
+
+static inline u32 calc_unconsumed_bytes(const volatile struct t_buf *buf)
{
- int x = buf->prod - buf->cons;
+ u32 prod = buf->prod, cons = buf->cons;
+ s32 x = prod - cons;
+
+ if ( bogus(prod, cons) )
+ return data_size;
+
if ( x < 0 )
x += 2*data_size;
@@ -426,9 +450,14 @@ static inline int calc_unconsumed_bytes(
return x;
}
-static inline int calc_bytes_to_wrap(struct t_buf *buf)
+static inline u32 calc_bytes_to_wrap(const volatile struct t_buf *buf)
{
- int x = data_size - buf->prod;
+ u32 prod = buf->prod;
+ s32 x = data_size - prod;
+
+ if ( bogus(prod, buf->cons) )
+ return 0;
+
if ( x <= 0 )
x += data_size;
@@ -438,35 +467,37 @@ static inline int calc_bytes_to_wrap(str
return x;
}
-static inline int calc_bytes_avail(struct t_buf *buf)
+static inline u32 calc_bytes_avail(const volatile struct t_buf *buf)
{
return data_size - calc_unconsumed_bytes(buf);
}
-static inline struct t_rec *
-next_record(struct t_buf *buf)
+static inline struct t_rec *next_record(const volatile struct t_buf *buf)
{
- int x = buf->prod;
+ u32 x = buf->prod;
+
+ if ( !tb_init_done || bogus(x, buf->cons) )
+ return NULL;
+
if ( x >= data_size )
x -= data_size;
- ASSERT(x >= 0);
ASSERT(x < data_size);
return (struct t_rec *)&this_cpu(t_data)[x];
}
-static inline int __insert_record(struct t_buf *buf,
- unsigned long event,
- int extra,
- int cycles,
- int rec_size,
- unsigned char *extra_data)
+static inline void __insert_record(volatile struct t_buf *buf,
+ unsigned long event,
+ unsigned int extra,
+ bool_t cycles,
+ unsigned int rec_size,
+ const void *extra_data)
{
struct t_rec *rec;
unsigned char *dst;
- unsigned long extra_word = extra/sizeof(u32);
- int local_rec_size = calc_rec_size(cycles, extra);
+ unsigned int extra_word = extra / sizeof(u32);
+ unsigned int local_rec_size = calc_rec_size(cycles, extra);
uint32_t next;
BUG_ON(local_rec_size != rec_size);
@@ -475,17 +506,20 @@ static inline int __insert_record(struct
/* Double-check once more that we have enough space.
* Don't bugcheck here, in case the userland tool is doing
* something stupid. */
- if ( calc_bytes_avail(buf) < rec_size )
+ next = calc_bytes_avail(buf);
+ if ( next < rec_size )
{
- printk("%s: %u bytes left (%u - ((%u - %u) %% %u) recsize %u.\n",
- __func__,
- calc_bytes_avail(buf),
- data_size, buf->prod, buf->cons, data_size, rec_size);
- return 0;
+ if ( printk_ratelimit() )
+ printk(XENLOG_WARNING
+ "%s: avail=%u (size=%08x prod=%08x cons=%08x) rec=%u\n",
+ __func__, next, data_size, buf->prod, buf->cons, rec_size);
+ return;
}
rmb();
rec = next_record(buf);
+ if ( !rec )
+ return;
rec->event = event;
rec->extra_u32 = extra_word;
dst = (unsigned char *)rec->u.nocycles.extra_u32;
@@ -502,21 +536,22 @@ static inline int __insert_record(struct
wmb();
- next = buf->prod + rec_size;
+ next = buf->prod;
+ if ( bogus(next, buf->cons) )
+ return;
+ next += rec_size;
if ( next >= 2*data_size )
next -= 2*data_size;
- ASSERT(next >= 0);
ASSERT(next < 2*data_size);
buf->prod = next;
-
- return rec_size;
}
-static inline int insert_wrap_record(struct t_buf *buf, int size)
+static inline void insert_wrap_record(volatile struct t_buf *buf,
+ unsigned int size)
{
- int space_left = calc_bytes_to_wrap(buf);
- unsigned long extra_space = space_left - sizeof(u32);
- int cycles = 0;
+ u32 space_left = calc_bytes_to_wrap(buf);
+ unsigned int extra_space = space_left - sizeof(u32);
+ bool_t cycles = 0;
BUG_ON(space_left > size);
@@ -528,17 +563,13 @@ static inline int insert_wrap_record(str
ASSERT((extra_space/sizeof(u32)) <= TRACE_EXTRA_MAX);
}
- return __insert_record(buf,
- TRC_TRACE_WRAP_BUFFER,
- extra_space,
- cycles,
- space_left,
- NULL);
+ __insert_record(buf, TRC_TRACE_WRAP_BUFFER, extra_space, cycles,
+ space_left, NULL);
}
#define LOST_REC_SIZE (4 + 8 + 16) /* header + tsc + sizeof(struct ed) */
-static inline int insert_lost_records(struct t_buf *buf)
+static inline void insert_lost_records(volatile struct t_buf *buf)
{
struct {
u32 lost_records;
@@ -553,12 +584,8 @@ static inline int insert_lost_records(st
this_cpu(lost_records) = 0;
- return __insert_record(buf,
- TRC_LOST_RECORDS,
- sizeof(ed),
- 1 /* cycles */,
- LOST_REC_SIZE,
- (unsigned char *)&ed);
+ __insert_record(buf, TRC_LOST_RECORDS, sizeof(ed), 1 /* cycles */,
+ LOST_REC_SIZE, &ed);
}
/*
@@ -580,13 +607,15 @@ static DECLARE_TASKLET(trace_notify_dom0
* failure, otherwise 0. Failure occurs only if the trace buffers are not yet
* initialised.
*/
-void __trace_var(u32 event, int cycles, int extra, unsigned char *extra_data)
+void __trace_var(u32 event, bool_t cycles, unsigned int extra,
+ const void *extra_data)
{
- struct t_buf *buf;
- unsigned long flags, bytes_to_tail, bytes_to_wrap;
- int rec_size, total_size;
- int extra_word;
- int started_below_highwater = 0;
+ volatile struct t_buf *buf;
+ unsigned long flags;
+ u32 bytes_to_tail, bytes_to_wrap;
+ unsigned int rec_size, total_size;
+ unsigned int extra_word;
+ bool_t started_below_highwater;
if( !tb_init_done )
return;
@@ -619,13 +648,11 @@ void __trace_var(u32 event, int cycles,
/* Read tb_init_done /before/ t_bufs. */
rmb();
-
- spin_lock_irqsave(&this_cpu(t_lock), flags);
-
buf = this_cpu(t_bufs);
-
if ( unlikely(!buf) )
- goto unlock;
+ return;
+
+ spin_lock_irqsave(&this_cpu(t_lock), flags);
started_below_highwater = (calc_unconsumed_bytes(buf) < t_buf_highwater);
--- 2010-06-15.orig/xen/include/xen/trace.h 2010-06-28 09:43:58.000000000
+0200
+++ 2010-06-15/xen/include/xen/trace.h 2010-06-25 12:08:36.000000000 +0200
@@ -36,7 +36,7 @@ int tb_control(struct xen_sysctl_tbuf_op
int trace_will_trace_event(u32 event);
-void __trace_var(u32 event, int cycles, int extra, unsigned char *extra_data);
+void __trace_var(u32 event, bool_t cycles, unsigned int extra, const void *);
static inline void trace_var(u32 event, int cycles, int extra,
unsigned char *extra_data)
@@ -57,7 +57,7 @@ static inline void trace_var(u32 event,
{ \
u32 _d[1]; \
_d[0] = d1; \
- __trace_var(_e, 1, sizeof(*_d), (unsigned char *)_d); \
+ __trace_var(_e, 1, sizeof(_d), _d); \
} \
} while ( 0 )
@@ -68,7 +68,7 @@ static inline void trace_var(u32 event,
u32 _d[2]; \
_d[0] = d1; \
_d[1] = d2; \
- __trace_var(_e, 1, sizeof(*_d)*2, (unsigned char *)_d); \
+ __trace_var(_e, 1, sizeof(_d), _d); \
} \
} while ( 0 )
@@ -80,7 +80,7 @@ static inline void trace_var(u32 event,
_d[0] = d1; \
_d[1] = d2; \
_d[2] = d3; \
- __trace_var(_e, 1, sizeof(*_d)*3, (unsigned char *)_d); \
+ __trace_var(_e, 1, sizeof(_d), _d); \
} \
} while ( 0 )
@@ -93,7 +93,7 @@ static inline void trace_var(u32 event,
_d[1] = d2; \
_d[2] = d3; \
_d[3] = d4; \
- __trace_var(_e, 1, sizeof(*_d)*4, (unsigned char *)_d); \
+ __trace_var(_e, 1, sizeof(_d), _d); \
} \
} while ( 0 )
@@ -107,7 +107,7 @@ static inline void trace_var(u32 event,
_d[2] = d3; \
_d[3] = d4; \
_d[4] = d5; \
- __trace_var(_e, 1, sizeof(*_d)*5, (unsigned char *)_d); \
+ __trace_var(_e, 1, sizeof(_d), _d); \
} \
} while ( 0 )
@@ -122,7 +122,7 @@ static inline void trace_var(u32 event,
_d[3] = d4; \
_d[4] = d5; \
_d[5] = d6; \
- __trace_var(_e, 1, sizeof(*_d)*6, (unsigned char *)_d); \
+ __trace_var(_e, 1, sizeof(_d), _d); \
} \
} while ( 0 )
trace-security.patch
Description: Text document
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