On Wed, Feb 21, 2024 at 02:46:21PM -0700, Nathan Chancellor wrote: > After a couple recent changes in LLVM, there is a warning (or error with > CONFIG_WERROR=y or W=e) from the compile time fortify source routines, > specifically the memset() in copy_to_user_tmpl(). > > In file included from net/xfrm/xfrm_user.c:14: > ... > include/linux/fortify-string.h:438:4: error: call to '__write_overflow_field' declared with 'warning' attribute: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror,-Wattribute-warning] > 438 | __write_overflow_field(p_size_field, size); > | ^ > 1 error generated. > > While ->xfrm_nr has been validated against XFRM_MAX_DEPTH when its value > is first assigned in copy_templates() by calling validate_tmpl() first > (so there should not be any issue in practice), LLVM/clang cannot really > deduce that across the boundaries of these functions. Without that > knowledge, it cannot assume that the loop stops before i is greater than > XFRM_MAX_DEPTH, which would indeed result a stack buffer overflow in the > memset(). > > To make the bounds of ->xfrm_nr clear to the compiler and add additional > defense in case copy_to_user_tmpl() is ever used in a path where > ->xfrm_nr has not been properly validated against XFRM_MAX_DEPTH first, > add an explicit bound check and early return, which clears up the > warning. > > Cc: stable@xxxxxxxxxxxxxxx > Link: https://github.com/ClangBuiltLinux/linux/issues/1985 > Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx> Applied to the ipsec tree, thanks a lot!
