Messages in this thread | | | From | Kees Cook <> | Date | Tue, 1 Aug 2017 11:20:26 -0700 | Subject | Re: [PATCH 2/2] adfs: use 'unsigned' types for memcpy length |
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On Tue, Aug 1, 2017 at 5:04 AM, Arnd Bergmann <arnd@arndb.de> wrote: > After commit 62d1034f53e3 ("fortify: use WARN instead of BUG for now"), we > get a warning in adfs about a possible buffer overflow: > > In function 'memcpy', > inlined from '__adfs_dir_put' at fs/adfs/dir_f.c:318:2, > inlined from 'adfs_f_update' at fs/adfs/dir_f.c:403:2: > include/linux/string.h:305:4: error: call to '__read_overflow2' declared with attribute error: detected read beyond size of object passed as 2nd parameter > __read_overflow2(); > ^~~~~~~~~~~~~~~~~~ > > The warning is correct in the sense that a negative 'pos' argument > to the function would have that result. However, this is not a bug, > as we know the position is always positive (in fact, between 5 > and 2007, inclusive) when the function gets called. > > Changing the variable to a unsigned type avoids the problem. I decided > to use 'unsigned int' for the position in the directory and the block > number, as they are both counting things, but use size_t for the > offset and length that get passed into memcpy. This shuts up the > warning. > > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Kees Cook <keescook@chromium.org>
Thanks for the fix! (Added sfr to Cc since he noticed this too.)
-Kees
-- Kees Cook Pixel Security
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