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authorAlexandre Chartre <alexandre.chartre@oracle.com>2024-06-20 16:47:47 +0200
committerJosh Poimboeuf <jpoimboe@kernel.org>2024-07-02 23:40:54 -0700
commit8e366d83edce3065ff3372bedc281c5e217c0550 (patch)
treee2d7ea29fa5624773cbebf9e106701ede727afe8 /drivers/net/wireguard/send.c
parentb13e9f6da4cc34240dae05418b9876b2758ebe35 (diff)
objtool/x86: objtool can confuse memory and stack access
The encoding of an x86 instruction can include a ModR/M and a SIB (Scale-Index-Base) byte to describe the addressing mode of the instruction. objtool processes all addressing mode with a SIB base of 5 as having %rbp as the base register. However, a SIB base of 5 means that the effective address has either no base (if ModR/M mod is zero) or %rbp as the base (if ModR/M mod is 1 or 2). This can cause objtool to confuse an absolute address access with a stack operation. For example, objtool will see the following instruction: 4c 8b 24 25 e0 ff ff mov 0xffffffffffffffe0,%r12 as a stack operation (i.e. similar to: mov -0x20(%rbp), %r12). [Note that this kind of weird absolute address access is added by the compiler when using KASAN.] If this perceived stack operation happens to reference the location where %r12 was pushed on the stack then the objtool validation will think that %r12 is being restored and this can cause a stack state mismatch. This kind behavior was seen on xfs code, after a minor change (convert kmem_alloc() to kmalloc()): >> fs/xfs/xfs.o: warning: objtool: xfs_da_grow_inode_int+0x6c1: stack state mismatch: reg1[12]=-2-48 reg2[12]=-1+0 Reported-by: kernel test robot <lkp@intel.com> Closes: https://lore.kernel.org/oe-kbuild-all/202402220435.MGN0EV6l-lkp@intel.com/ Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com> Link: https://lore.kernel.org/r/20240620144747.2524805-1-alexandre.chartre@oracle.com Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Diffstat (limited to 'drivers/net/wireguard/send.c')
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