From: Masami Hiramatsu mhiramat@kernel.org
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 keescook@chromium.org.
[ bp: Massage commit message, sync with the respective header in tools/ and drop "we". ]
Fixes: 2b1444983508 ("uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints") Reported-by: syzbot+9b64b619f10f19d19a7c@syzkaller.appspotmail.com Signed-off-by: Masami Hiramatsu mhiramat@kernel.org Signed-off-by: Borislav Petkov bp@suse.de Reviewed-by: Srikar Dronamraju srikar@linux.vnet.ibm.com Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/160697103739.3146288.7437620795200799020.stgit@dev... [sudip: adjust context, drop change of insn.h in tools] Signed-off-by: Sudip Mukherjee sudipm.mukherjee@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/include/asm/insn.h | 15 +++++++++++++++ arch/x86/kernel/uprobes.c | 10 ++++++---- 2 files changed, 21 insertions(+), 4 deletions(-)
--- a/arch/x86/include/asm/insn.h +++ b/arch/x86/include/asm/insn.h @@ -198,6 +198,21 @@ static inline int insn_offset_immediate( 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
--- a/arch/x86/kernel/uprobes.c +++ b/arch/x86/kernel/uprobes.c @@ -268,10 +268,11 @@ static volatile u32 good_2byte_insns[256
static bool is_prefix_bad(struct insn *insn) { + insn_byte_t p; int i;
- for (i = 0; i < insn->prefixes.nbytes; i++) { - switch (insn->prefixes.bytes[i]) { + for_each_insn_prefix(insn, i, p) { + switch (p) { case 0x26: /* INAT_PFX_ES */ case 0x2E: /* INAT_PFX_CS */ case 0x36: /* INAT_PFX_DS */ @@ -711,6 +712,7 @@ static struct uprobe_xol_ops branch_xol_ static int branch_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn) { u8 opc1 = OPCODE1(insn); + insn_byte_t p; int i;
switch (opc1) { @@ -741,8 +743,8 @@ static int branch_setup_xol_ops(struct a * Intel and AMD behavior differ in 64-bit mode: Intel ignores 66 prefix. * No one uses these insns, reject any branch insns with such prefix. */ - for (i = 0; i < insn->prefixes.nbytes; i++) { - if (insn->prefixes.bytes[i] == 0x66) + for_each_insn_prefix(insn, i, p) { + if (p == 0x66) return -ENOTSUPP; }