66 lines
2.2 KiB
Diff
66 lines
2.2 KiB
Diff
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xentrace: correct overflow check for number of per-cpu trace pages
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(xen-unstable changeset 23239:51d89366c859)
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The calculated number of per-cpu trace pages is stored in t_info and
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shared with tools like xentrace. Since its an u16 the value may overflow
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because the current check is based on u32.
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Using the u16 means each cpu could in theory use up to 256MB as trace
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buffer. However such a large allocation will currently fail on x86 due
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to the MAX_ORDER limit.
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Check both max theoretical number of pages per cpu and max number of
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pages reachable by struct t_buf->prod/cons variables with requested
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number of pages.
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Signed-off-by: Olaf Hering <olaf@aepfle.de>
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---
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xen/common/trace.c | 22 +++++++++++++++-------
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1 file changed, 15 insertions(+), 7 deletions(-)
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Index: xen-4.1.1-testing/xen/common/trace.c
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===================================================================
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--- xen-4.1.1-testing.orig/xen/common/trace.c
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+++ xen-4.1.1-testing/xen/common/trace.c
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@@ -105,25 +105,33 @@ static void calc_tinfo_first_offset(void
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* calculate_tbuf_size - check to make sure that the proposed size will fit
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* in the currently sized struct t_info and allows prod and cons to
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* reach double the value without overflow.
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+ * The t_info layout is fixed and cant be changed without breaking xentrace.
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* Initialize t_info_pages based on number of trace pages.
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*/
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static int calculate_tbuf_size(unsigned int pages)
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{
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- struct t_buf dummy;
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- typeof(dummy.prod) size;
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+ struct t_buf dummy_size;
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+ typeof(dummy_size.prod) max_size;
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+ struct t_info dummy_pages;
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+ typeof(dummy_pages.tbuf_size) max_pages;
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unsigned int t_info_words;
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/* force maximum value for an unsigned type */
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- size = -1;
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+ max_size = -1;
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+ max_pages = -1;
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/* max size holds up to n pages */
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- size /= PAGE_SIZE;
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- if ( pages > size )
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+ max_size /= PAGE_SIZE;
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+
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+ if ( max_size < max_pages )
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+ max_pages = max_size;
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+
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+ if ( pages > max_pages )
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{
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printk(XENLOG_INFO "xentrace: requested number of %u pages "
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"reduced to %u\n",
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- pages, (unsigned int)size);
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- pages = size;
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+ pages, max_pages);
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+ pages = max_pages;
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}
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t_info_words = num_online_cpus() * pages * sizeof(uint32_t);
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