* [PATCH -tip 0/2] x86/kprobes: Fix and cleanup can_boost()
@ 2021-03-25 10:08 Masami Hiramatsu
2021-03-25 10:08 ` [PATCH -tip 1/2] x86/kprobes: Fix to check non boostable prefixes correctly Masami Hiramatsu
2021-03-25 10:08 ` [PATCH -tip 2/2] x86/kprobes: Fix to identify indirect jmp and others using range case Masami Hiramatsu
0 siblings, 2 replies; 5+ messages in thread
From: Masami Hiramatsu @ 2021-03-25 10:08 UTC (permalink / raw)
To: Peter Zijlstra, Ingo Molnar
Cc: Thomas Gleixner, Ingo Molnar, Andy Lutomirski, Borislav Petkov,
x86, H . Peter Anvin, Masami Hiramatsu, linux-kernel,
kernel-janitors, Colin Ian King, dan.carpenter,
Muhammad Usama Anjum
Hi,
Here are 2 bugfixes for the x86/kprobes, [1/2] fixes an old bug which tries to find
instruction prefixes in insn->opcode (which should be never found) and misusing
insn->attr. [2/2] fixes a new bug found by Coverity in the recent commit 6256e668b7
("x86/kprobes: Use int3 instead of debug trap for single-step").
To fix the 2nd one, [2/2] also cleanup the switch-case with range cases, because
that is much more clear what is not boostable.
Thank you,
---
Masami Hiramatsu (2):
x86/kprobes: Fix to check non boostable prefixes correctly
x86/kprobes: Fix to identify indirect jmp and others using range case
arch/x86/kernel/kprobes/core.c | 57 +++++++++++++++++++++-------------------
1 file changed, 30 insertions(+), 27 deletions(-)
--
Masami Hiramatsu (Linaro) <mhiramat@kernel.org>
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH -tip 1/2] x86/kprobes: Fix to check non boostable prefixes correctly
2021-03-25 10:08 [PATCH -tip 0/2] x86/kprobes: Fix and cleanup can_boost() Masami Hiramatsu
@ 2021-03-25 10:08 ` Masami Hiramatsu
2021-03-25 11:08 ` [tip: x86/core] " tip-bot2 for Masami Hiramatsu
2021-03-25 10:08 ` [PATCH -tip 2/2] x86/kprobes: Fix to identify indirect jmp and others using range case Masami Hiramatsu
1 sibling, 1 reply; 5+ messages in thread
From: Masami Hiramatsu @ 2021-03-25 10:08 UTC (permalink / raw)
To: Peter Zijlstra, Ingo Molnar
Cc: Thomas Gleixner, Ingo Molnar, Andy Lutomirski, Borislav Petkov,
x86, H . Peter Anvin, Masami Hiramatsu, linux-kernel,
kernel-janitors, Colin Ian King, dan.carpenter,
Muhammad Usama Anjum
There are 2 bugs in the can_boost() function because of using
x86 insn decoder. Since the insn->opcode never has a prefix byte,
it can not find CS override prefix in it. And the insn->attr is
the attribute of the opcode, thus inat_is_address_size_prefix(
insn->attr) always returns false.
Fix those by checking each prefix bytes with for_each_insn_prefix
loop and getting the correct attribute for each prefix byte.
Also, this removes unlikely, because this is a slow path.
Fixes: a8d11cd0714f ("kprobes/x86: Consolidate insn decoder users for copying code")
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
arch/x86/kernel/kprobes/core.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 89d9f26785c7..503958f15cf9 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -139,6 +139,8 @@ NOKPROBE_SYMBOL(synthesize_relcall);
int can_boost(struct insn *insn, void *addr)
{
kprobe_opcode_t opcode;
+ insn_byte_t prefix;
+ int i;
if (search_exception_tables((unsigned long)addr))
return 0; /* Page fault may occur on this address. */
@@ -151,9 +153,14 @@ int can_boost(struct insn *insn, void *addr)
if (insn->opcode.nbytes != 1)
return 0;
- /* Can't boost Address-size override prefix */
- if (unlikely(inat_is_address_size_prefix(insn->attr)))
- return 0;
+ for_each_insn_prefix(insn, i, prefix) {
+ insn_attr_t attr;
+
+ attr = inat_get_opcode_attribute(prefix);
+ /* Can't boost Address-size override prefix and CS override prefix */
+ if (prefix == 0x2e || inat_is_address_size_prefix(attr))
+ return 0;
+ }
opcode = insn->opcode.bytes[0];
@@ -181,8 +188,8 @@ int can_boost(struct insn *insn, void *addr)
/* indirect jmp is boostable */
return X86_MODRM_REG(insn->modrm.bytes[0]) == 4;
default:
- /* CS override prefix and call are not boostable */
- return (opcode != 0x2e && opcode != 0x9a);
+ /* call is not boostable */
+ return opcode != 0x9a;
}
}
^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH -tip 2/2] x86/kprobes: Fix to identify indirect jmp and others using range case
2021-03-25 10:08 [PATCH -tip 0/2] x86/kprobes: Fix and cleanup can_boost() Masami Hiramatsu
2021-03-25 10:08 ` [PATCH -tip 1/2] x86/kprobes: Fix to check non boostable prefixes correctly Masami Hiramatsu
@ 2021-03-25 10:08 ` Masami Hiramatsu
2021-03-25 11:08 ` [tip: x86/core] " tip-bot2 for Masami Hiramatsu
1 sibling, 1 reply; 5+ messages in thread
From: Masami Hiramatsu @ 2021-03-25 10:08 UTC (permalink / raw)
To: Peter Zijlstra, Ingo Molnar
Cc: Thomas Gleixner, Ingo Molnar, Andy Lutomirski, Borislav Petkov,
x86, H . Peter Anvin, Masami Hiramatsu, linux-kernel,
kernel-janitors, Colin Ian King, dan.carpenter,
Muhammad Usama Anjum
Fix can_boost() to identify indirect jmp and others using range case
correctly.
Since the condition in switch statement is opcode & 0xf0, it can not
evaluate to 0xff case. This should be under the 0xf0 case. However,
there is no reason to use the conbinations of the bit-masked condition
and lower bit checking.
Use range case to clean up the switch statement too.
Fixes: 6256e668b7 ("x86/kprobes: Use int3 instead of debug trap for single-step")
Reported-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
arch/x86/kernel/kprobes/core.c | 44 ++++++++++++++++++----------------------
1 file changed, 20 insertions(+), 24 deletions(-)
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 503958f15cf9..c1c763840d6e 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -164,32 +164,28 @@ int can_boost(struct insn *insn, void *addr)
opcode = insn->opcode.bytes[0];
- switch (opcode & 0xf0) {
- case 0x60:
- /* can't boost "bound" */
- return (opcode != 0x62);
- case 0x70:
- return 0; /* can't boost conditional jump */
- case 0x90:
- return opcode != 0x9a; /* can't boost call far */
- case 0xc0:
- /* can't boost software-interruptions */
- return (0xc1 < opcode && opcode < 0xcc) || opcode == 0xcf;
- case 0xd0:
- /* can boost AA* and XLAT */
- return (opcode == 0xd4 || opcode == 0xd5 || opcode == 0xd7);
- case 0xe0:
- /* can boost in/out and absolute jmps */
- return ((opcode & 0x04) || opcode == 0xea);
- case 0xf0:
- /* clear and set flags are boostable */
- return (opcode == 0xf5 || (0xf7 < opcode && opcode < 0xfe));
- case 0xff:
- /* indirect jmp is boostable */
+ switch (opcode) {
+ case 0x62: /* bound */
+ case 0x70 ... 0x7f: /* Conditional jumps */
+ case 0x9a: /* Call far */
+ case 0xc0 ... 0xc1: /* Grp2 */
+ case 0xcc ... 0xce: /* software exceptions */
+ case 0xd0 ... 0xd3: /* Grp2 */
+ case 0xd6: /* (UD) */
+ case 0xd8 ... 0xdf: /* ESC */
+ case 0xe0 ... 0xe3: /* LOOP*, JCXZ */
+ case 0xe8 ... 0xe9: /* near Call, JMP */
+ case 0xeb: /* Short JMP */
+ case 0xf0 ... 0xf4: /* LOCK/REP, HLT */
+ case 0xf6 ... 0xf7: /* Grp3 */
+ case 0xfe: /* Grp4 */
+ /* ... are not boostable */
+ return 0;
+ case 0xff: /* Grp5 */
+ /* Only indirect jmp is boostable */
return X86_MODRM_REG(insn->modrm.bytes[0]) == 4;
default:
- /* call is not boostable */
- return opcode != 0x9a;
+ return 1;
}
}
^ permalink raw reply related [flat|nested] 5+ messages in thread
* [tip: x86/core] x86/kprobes: Fix to identify indirect jmp and others using range case
2021-03-25 10:08 ` [PATCH -tip 2/2] x86/kprobes: Fix to identify indirect jmp and others using range case Masami Hiramatsu
@ 2021-03-25 11:08 ` tip-bot2 for Masami Hiramatsu
0 siblings, 0 replies; 5+ messages in thread
From: tip-bot2 for Masami Hiramatsu @ 2021-03-25 11:08 UTC (permalink / raw)
To: linux-tip-commits
Cc: Colin Ian King, Masami Hiramatsu, Ingo Molnar, x86, linux-kernel
The following commit has been merged into the x86/core branch of tip:
Commit-ID: 2f706e0e5e263c0d204e37ea496cbb0e98aac2d2
Gitweb: https://git.kernel.org/tip/2f706e0e5e263c0d204e37ea496cbb0e98aac2d2
Author: Masami Hiramatsu <mhiramat@kernel.org>
AuthorDate: Thu, 25 Mar 2021 19:08:43 +09:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Thu, 25 Mar 2021 11:37:22 +01:00
x86/kprobes: Fix to identify indirect jmp and others using range case
Fix can_boost() to identify indirect jmp and others using range case
correctly.
Since the condition in switch statement is opcode & 0xf0, it can not
evaluate to 0xff case. This should be under the 0xf0 case. However,
there is no reason to use the conbinations of the bit-masked condition
and lower bit checking.
Use range case to clean up the switch statement too.
Fixes: 6256e668b7 ("x86/kprobes: Use int3 instead of debug trap for single-step")
Reported-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/161666692308.1120877.4675552834049546493.stgit@devnote2
---
arch/x86/kernel/kprobes/core.c | 44 +++++++++++++++------------------
1 file changed, 20 insertions(+), 24 deletions(-)
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 81e1432..922a6e2 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -164,32 +164,28 @@ int can_boost(struct insn *insn, void *addr)
opcode = insn->opcode.bytes[0];
- switch (opcode & 0xf0) {
- case 0x60:
- /* can't boost "bound" */
- return (opcode != 0x62);
- case 0x70:
- return 0; /* can't boost conditional jump */
- case 0x90:
- return opcode != 0x9a; /* can't boost call far */
- case 0xc0:
- /* can't boost software-interruptions */
- return (0xc1 < opcode && opcode < 0xcc) || opcode == 0xcf;
- case 0xd0:
- /* can boost AA* and XLAT */
- return (opcode == 0xd4 || opcode == 0xd5 || opcode == 0xd7);
- case 0xe0:
- /* can boost in/out and absolute jmps */
- return ((opcode & 0x04) || opcode == 0xea);
- case 0xf0:
- /* clear and set flags are boostable */
- return (opcode == 0xf5 || (0xf7 < opcode && opcode < 0xfe));
- case 0xff:
- /* indirect jmp is boostable */
+ switch (opcode) {
+ case 0x62: /* bound */
+ case 0x70 ... 0x7f: /* Conditional jumps */
+ case 0x9a: /* Call far */
+ case 0xc0 ... 0xc1: /* Grp2 */
+ case 0xcc ... 0xce: /* software exceptions */
+ case 0xd0 ... 0xd3: /* Grp2 */
+ case 0xd6: /* (UD) */
+ case 0xd8 ... 0xdf: /* ESC */
+ case 0xe0 ... 0xe3: /* LOOP*, JCXZ */
+ case 0xe8 ... 0xe9: /* near Call, JMP */
+ case 0xeb: /* Short JMP */
+ case 0xf0 ... 0xf4: /* LOCK/REP, HLT */
+ case 0xf6 ... 0xf7: /* Grp3 */
+ case 0xfe: /* Grp4 */
+ /* ... are not boostable */
+ return 0;
+ case 0xff: /* Grp5 */
+ /* Only indirect jmp is boostable */
return X86_MODRM_REG(insn->modrm.bytes[0]) == 4;
default:
- /* call is not boostable */
- return opcode != 0x9a;
+ return 1;
}
}
^ permalink raw reply related [flat|nested] 5+ messages in thread
* [tip: x86/core] x86/kprobes: Fix to check non boostable prefixes correctly
2021-03-25 10:08 ` [PATCH -tip 1/2] x86/kprobes: Fix to check non boostable prefixes correctly Masami Hiramatsu
@ 2021-03-25 11:08 ` tip-bot2 for Masami Hiramatsu
0 siblings, 0 replies; 5+ messages in thread
From: tip-bot2 for Masami Hiramatsu @ 2021-03-25 11:08 UTC (permalink / raw)
To: linux-tip-commits; +Cc: Masami Hiramatsu, Ingo Molnar, x86, linux-kernel
The following commit has been merged into the x86/core branch of tip:
Commit-ID: 6dd3b8c9f58816a1354be39559f630cd1bd12159
Gitweb: https://git.kernel.org/tip/6dd3b8c9f58816a1354be39559f630cd1bd12159
Author: Masami Hiramatsu <mhiramat@kernel.org>
AuthorDate: Thu, 25 Mar 2021 19:08:31 +09:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Thu, 25 Mar 2021 11:37:21 +01:00
x86/kprobes: Fix to check non boostable prefixes correctly
There are 2 bugs in the can_boost() function because of using
x86 insn decoder. Since the insn->opcode never has a prefix byte,
it can not find CS override prefix in it. And the insn->attr is
the attribute of the opcode, thus inat_is_address_size_prefix(
insn->attr) always returns false.
Fix those by checking each prefix bytes with for_each_insn_prefix
loop and getting the correct attribute for each prefix byte.
Also, this removes unlikely, because this is a slow path.
Fixes: a8d11cd0714f ("kprobes/x86: Consolidate insn decoder users for copying code")
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/161666691162.1120877.2808435205294352583.stgit@devnote2
---
arch/x86/kernel/kprobes/core.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 3a14e8a..81e1432 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -139,6 +139,8 @@ NOKPROBE_SYMBOL(synthesize_relcall);
int can_boost(struct insn *insn, void *addr)
{
kprobe_opcode_t opcode;
+ insn_byte_t prefix;
+ int i;
if (search_exception_tables((unsigned long)addr))
return 0; /* Page fault may occur on this address. */
@@ -151,9 +153,14 @@ int can_boost(struct insn *insn, void *addr)
if (insn->opcode.nbytes != 1)
return 0;
- /* Can't boost Address-size override prefix */
- if (unlikely(inat_is_address_size_prefix(insn->attr)))
- return 0;
+ for_each_insn_prefix(insn, i, prefix) {
+ insn_attr_t attr;
+
+ attr = inat_get_opcode_attribute(prefix);
+ /* Can't boost Address-size override prefix and CS override prefix */
+ if (prefix == 0x2e || inat_is_address_size_prefix(attr))
+ return 0;
+ }
opcode = insn->opcode.bytes[0];
@@ -181,8 +188,8 @@ int can_boost(struct insn *insn, void *addr)
/* indirect jmp is boostable */
return X86_MODRM_REG(insn->modrm.bytes[0]) == 4;
default:
- /* CS override prefix and call are not boostable */
- return (opcode != 0x2e && opcode != 0x9a);
+ /* call is not boostable */
+ return opcode != 0x9a;
}
}
^ permalink raw reply related [flat|nested] 5+ messages in thread
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2021-03-25 10:08 [PATCH -tip 0/2] x86/kprobes: Fix and cleanup can_boost() Masami Hiramatsu
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2021-03-25 11:08 ` [tip: x86/core] " tip-bot2 for Masami Hiramatsu
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