[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH for-4.10] string: fix memmove when size is 0
ubsan in clang 5.0 complains with: (XEN) UBSAN: Undefined behaviour in string.c:50:28 (XEN) pointer overflow: (XEN) addition of unsigned offset to ffff830000100000 overflowed to ffff8300000fffff [...] (XEN) Xen call trace: (XEN) [<ffff82d0802dce0d>] ubsan.c#ubsan_epilogue+0xd/0xc0 (XEN) [<ffff82d0802de145>] __ubsan_handle_pointer_overflow+0xa5/0xe0 (XEN) [<ffff82d0803bf627>] memmove+0x67/0x80 (XEN) [<ffff82d080679f87>] page_alloc.c#bootmem_region_add+0x157/0x220 (XEN) [<ffff82d080679c66>] init_boot_pages+0x56/0x220 (XEN) [<ffff82d0806bcb9d>] __start_xen+0x2c2d/0x4b50 (XEN) [<ffff82d0802000f3>] __high_start+0x53/0x60 This is due to memmove doing a n-1+addr when n is 0. This is harmless because the loop is bounded to 0. Fix this by returning earlier when n is 0. Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx> --- Cc: Jan Beulich <jbeulich@xxxxxxxx> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> Cc: Julien Grall <julien.grall@xxxxxxx> --- This is a harmless fix that shouldn't introduce any functional change, and hence it should be committed to 4.10 IMHO. --- xen/arch/x86/string.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/xen/arch/x86/string.c b/xen/arch/x86/string.c index cd85a38e6d..19dcfe88ed 100644 --- a/xen/arch/x86/string.c +++ b/xen/arch/x86/string.c @@ -39,6 +39,9 @@ void *(memmove)(void *dest, const void *src, size_t n) { long d0, d1, d2; + if ( !n ) + return; + if ( dest < src ) return memcpy(dest, src, n); -- 2.13.5 (Apple Git-94) _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel
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