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authorRich Felker <dalias@aerifal.cx>2016-10-19 20:17:16 -0400
committerRich Felker <dalias@aerifal.cx>2016-10-19 20:17:16 -0400
commit70d2687d85c314963cf280759b23fd4573ff0d82 (patch)
treedbbd4b169245294bee78e30f33e1cc22c519be3d /src/stdio/rename.c
parentaee6abb2400b9a955c2b41166db1c22f63ad42ef (diff)
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fix integer overflow in float printf needed-precision computation
if the requested precision is close to INT_MAX, adding
LDBL_MANT_DIG/3+8 overflows. in practice the resulting undefined
behavior manifests as a large negative result, which is then used to
compute the new end pointer (z) with a wildly out-of-bounds value
(more overflow, more undefined behavior). the end result is at least
incorrect output and character count (return value); worse things do
not seem to happen, but detailed analysis has not been done.

this patch fixes the overflow by performing the intermediate
computation as unsigned; after division by 9, the final result
necessarily fits in int.
Diffstat (limited to 'src/stdio/rename.c')
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