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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH 4 of 4] trace: fix security issues
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), I figured that the hypervisor shouldn't rely on any
specific state of the actual trace buffer (as it is shared writable with
Dom0)
[GWD: Volatile quantifiers have been taken out and moved to another patch]
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>
Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
diff -r 16ccc9071662 -r ad8596271373 xen/common/trace.c
--- a/xen/common/trace.c Thu Jul 01 11:09:49 2010 +0100
+++ b/xen/common/trace.c Thu Jul 01 11:09:49 2010 +0100
@@ -53,12 +53,12 @@
static DEFINE_PER_CPU_READ_MOSTLY(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;
static u32 t_info_first_offset __read_mostly;
/* 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);
@@ -163,7 +163,7 @@
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);
@@ -214,6 +214,7 @@
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);
}
@@ -432,19 +433,37 @@
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)
{
- int x = buf->prod - buf->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 struct t_buf *buf)
+{
+ 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;
@@ -454,9 +473,14 @@
return x;
}
-static inline int calc_bytes_to_wrap(struct t_buf *buf)
+static inline u32 calc_bytes_to_wrap(const 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;
@@ -466,35 +490,37 @@
return x;
}
-static inline int calc_bytes_avail(struct t_buf *buf)
+static inline u32 calc_bytes_avail(const 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 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(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);
@@ -510,11 +536,13 @@
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 0;
+ 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;
@@ -531,21 +559,22 @@
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(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);
@@ -557,17 +586,13 @@
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(struct t_buf *buf)
{
struct {
u32 lost_records;
@@ -582,12 +607,8 @@
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);
}
/*
@@ -609,13 +630,15 @@
* 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;
+ 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;
@@ -654,7 +677,11 @@
buf = this_cpu(t_bufs);
if ( unlikely(!buf) )
+ {
+ /* Make gcc happy */
+ started_below_highwater = 0;
goto unlock;
+ }
started_below_highwater = (calc_unconsumed_bytes(buf) < t_buf_highwater);
@@ -735,8 +762,9 @@
spin_unlock_irqrestore(&this_cpu(t_lock), flags);
/* Notify trace buffer consumer that we've crossed the high water mark. */
- if ( started_below_highwater &&
- (calc_unconsumed_bytes(buf) >= t_buf_highwater) )
+ if ( likely(buf!=NULL)
+ && started_below_highwater
+ && (calc_unconsumed_bytes(buf) >= t_buf_highwater) )
tasklet_schedule(&trace_notify_dom0_tasklet);
}
diff -r 16ccc9071662 -r ad8596271373 xen/include/xen/trace.h
--- a/xen/include/xen/trace.h Thu Jul 01 11:09:49 2010 +0100
+++ b/xen/include/xen/trace.h Thu Jul 01 11:09:49 2010 +0100
@@ -36,7 +36,7 @@
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 @@
{ \
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 @@
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 @@
_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 @@
_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 @@
_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 @@
_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 )
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