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x86/uprobes: Do not use prefixes.nbytes when looping over prefixes.bytes

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commit 4e9a5ae8df5b3365183150f6df49e49dece80d8c upstream.

Since insn.prefixes.nbytes can be bigger than the size of
insn.prefixes.bytes[] when a prefix is repeated, the proper check must
be

  insn.prefixes.bytes[i] != 0 and i < 4

instead of using insn.prefixes.nbytes.

Introduce a for_each_insn_prefix() macro for this purpose. Debugged by
Kees Cook <[email protected]>.

 [ bp: Massage commit message, sync with the respective header in tools/
   and drop "we". ]

Fixes: 2b14449835 ("uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints")
Reported-by: [email protected]
Signed-off-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Reviewed-by: Srikar Dronamraju <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/160697103739.3146288.7437620795200799020.stgit@devnote2
Signed-off-by: Greg Kroah-Hartman <[email protected]>
This commit is contained in:
Masami Hiramatsu 2020-12-03 13:50:37 +09:00 • committed by Greg Kroah-Hartman
commit 579c977253
3 changed files with 36 additions and 4 deletions
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15
tools/arch/x86/include/asm/insn.h
View file

@ -195,6 +195,21 @@ static inline int insn_offset_immediate(struct insn *insn)
return insn_offset_displacement(insn) + insn->displacement.nbytes;
}
/**
* for_each_insn_prefix() -- Iterate prefixes in the instruction
* @insn: Pointer to struct insn.
* @idx: Index storage.
* @prefix: Prefix byte.
*
* Iterate prefix bytes of given @insn. Each prefix byte is stored in @prefix
* and the index is stored in @idx (note that this @idx is just for a cursor,
* do not change it.)
* Since prefixes.nbytes can be bigger than 4 if some prefixes
* are repeated, it cannot be used for looping over the prefixes.
*/
#define for_each_insn_prefix(insn, idx, prefix) \
for (idx = 0; idx < ARRAY_SIZE(insn->prefixes.bytes) && (prefix = insn->prefixes.bytes[idx]) != 0; idx++)
#define POP_SS_OPCODE 0x1f
#define MOV_SREG_OPCODE 0x8e