[syzbot] [bpf?] [net?] KMSAN: uninit-value in dev_map_hash_lookup_elem

[syzbot] [bpf?] [net?] KMSAN: uninit-value in dev_map_hash_lookup_elem

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    614da38e2f7a Merge tag 'hid-for-linus-2024051401' of git:/..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1429a96c980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f5d2cbf33633f507
dashboard link: https://syzkaller.appspot.com/bug?extid=80cf9d55d6fd2d6a9838
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16a53ae4980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=113003d4980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/89eafb874b71/disk-614da38e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/356000512ad9/vmlinux-614da38e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/839c73939115/bzImage-614da38e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+80cf9d55d6fd2d6a9838@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in __dev_map_hash_lookup_elem kernel/bpf/devmap.c:270 [inline]
BUG: KMSAN: uninit-value in dev_map_hash_lookup_elem+0x116/0x2e0 kernel/bpf/devmap.c:803
 __dev_map_hash_lookup_elem kernel/bpf/devmap.c:270 [inline]
 dev_map_hash_lookup_elem+0x116/0x2e0 kernel/bpf/devmap.c:803
 ____bpf_map_lookup_elem kernel/bpf/helpers.c:42 [inline]
 bpf_map_lookup_elem+0x5c/0x80 kernel/bpf/helpers.c:38
 ___bpf_prog_run+0x13fe/0xe0f0 kernel/bpf/core.c:1997
 __bpf_prog_run64+0xb5/0xe0 kernel/bpf/core.c:2236
 bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
 __bpf_prog_run include/linux/filter.h:657 [inline]
 bpf_prog_run include/linux/filter.h:664 [inline]
 __bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
 bpf_trace_run4+0x150/0x340 kernel/trace/bpf_trace.c:2422
 __bpf_trace_sched_switch+0x37/0x50 include/trace/events/sched.h:222
 trace_sched_switch include/trace/events/sched.h:222 [inline]
 __schedule+0x2eca/0x6bc0 kernel/sched/core.c:6743
 __schedule_loop kernel/sched/core.c:6823 [inline]
 schedule+0x13d/0x380 kernel/sched/core.c:6838
 ptrace_stop+0x8eb/0xd60 kernel/signal.c:2358
 ptrace_do_notify kernel/signal.c:2395 [inline]
 ptrace_notify+0x234/0x320 kernel/signal.c:2407
 ptrace_report_syscall include/linux/ptrace.h:415 [inline]
 ptrace_report_syscall_exit include/linux/ptrace.h:477 [inline]
 syscall_exit_work+0x14e/0x3e0 kernel/entry/common.c:173
 syscall_exit_to_user_mode_prepare kernel/entry/common.c:200 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:205 [inline]
 syscall_exit_to_user_mode+0x135/0x160 kernel/entry/common.c:218
 do_syscall_64+0xdc/0x1e0 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Local variable stack created at:
 __bpf_prog_run64+0x45/0xe0 kernel/bpf/core.c:2236
 bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
 __bpf_prog_run include/linux/filter.h:657 [inline]
 bpf_prog_run include/linux/filter.h:664 [inline]
 __bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
 bpf_trace_run4+0x150/0x340 kernel/trace/bpf_trace.c:2422

CPU: 0 PID: 5042 Comm: syz-executor593 Not tainted 6.9.0-syzkaller-02707-g614da38e2f7a #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
=====================================================


---
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If the report is already addressed, let syzbot know by replying with:
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#syz undup

Re: [syzbot] [syzbot] [bpf?] [net?] KMSAN: uninit-value in dev_map_hash_lookup_elem

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: [syzbot] [bpf?] [net?] KMSAN: uninit-value in dev_map_hash_lookup_elem
Author: wojciech.gladysz@infogain.com

#syz test: https://linux.googlesource.com/linux/kernel/git/torvalds/linux e478cf26c556e4ab572ab0ab2306c986901dcd61

---
 kernel/bpf/verifier.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 36ef8e96787e..13a9c2e2908a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7146,8 +7146,8 @@ static int check_stack_range_initialized(
 		 * reads. However, if raw_mode is not set, we'll do extra
 		 * checks below.
 		 */
-		bounds_check_type = BPF_WRITE;
-		clobber = true;
+		clobber = !meta || meta->raw_mode;
+		bounds_check_type = clobber ? BPF_WRITE : BPF_READ;
 	} else {
 		bounds_check_type = BPF_READ;
 	}
@@ -7230,8 +7230,7 @@ static int check_stack_range_initialized(
 		stype = &state->stack[spi].slot_type[slot % BPF_REG_SIZE];
 		if (*stype == STACK_MISC)
 			goto mark;
-		if ((*stype == STACK_ZERO) ||
-		    (*stype == STACK_INVALID && env->allow_uninit_stack)) {
+		if (*stype == STACK_ZERO) {
 			if (clobber) {
 				/* helper can write anything into the stack */
 				*stype = STACK_MISC;
@@ -8748,6 +8747,8 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 		meta->map_uid = reg->map_uid;
 		break;
 	case ARG_PTR_TO_MAP_KEY:
+		/* always mark read access */
+		meta->raw_mode = false;
 		/* bpf_map_xxx(..., map_ptr, ..., key) call:
 		 * check that [key, key + map->key_size) are within
 		 * stack limits and initialized
@@ -8763,7 +8764,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 		}
 		err = check_helper_mem_access(env, regno,
 					      meta->map_ptr->key_size, false,
-					      NULL);
+					      meta);
 		break;
 	case ARG_PTR_TO_MAP_VALUE:
 		if (type_may_be_null(arg_type) && register_is_null(reg))
-- 
2.35.3

Re: [syzbot] [bpf?] [net?] KMSAN: uninit-value in dev_map_hash_lookup_elem

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
SYZFAIL: NL802154_CMD_SET_SHORT_ADDR failed

2024/07/01 12:26:06 ignoring optional flag "sandboxArg"="0"
2024/07/01 12:26:07 parsed 1 programs
2024/07/01 12:26:07 [FATAL] failed to run ["./syz-executor" "setup" "fault" "binfmt_misc" "usb" "802154" "swap"]: exit status 67
mkdir(/syzcgroup) failed: 17
mount(binfmt_misc) failed: 16
SYZFAIL: NL802154_CMD_SET_SHORT_ADDR failed
 (errno 16: Device or resource busy)


Tested on:

commit:         e478cf26 Merge branch 'bpf-fix-a-couple-of-test-failur..
git tree:       https://linux.googlesource.com/linux/kernel/git/torvalds/linux
console output: https://syzkaller.appspot.com/x/log.txt?x=15f181c1980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2ad6a8768920dd4b
dashboard link: https://syzkaller.appspot.com/bug?extid=80cf9d55d6fd2d6a9838
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=129891d1980000

Re: [syzbot] [syzbot] [bpf?] [net?] KMSAN: uninit-value in dev_map_hash_lookup_elem

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: [syzbot] [bpf?] [net?] KMSAN: uninit-value in dev_map_hash_lookup_elem
Author: wojciech.gladysz@infogain.com

#syz test: https://linux.googlesource.com/linux/kernel/git/torvalds/linux e478cf26c556e4ab572ab0ab2306c986901dcd61

---
 kernel/bpf/verifier.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 36ef8e96787e..13a9c2e2908a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7146,8 +7146,8 @@ static int check_stack_range_initialized(
 		 * reads. However, if raw_mode is not set, we'll do extra
 		 * checks below.
 		 */
-		bounds_check_type = BPF_WRITE;
-		clobber = true;
+		clobber = !meta || meta->raw_mode;
+		bounds_check_type = clobber ? BPF_WRITE : BPF_READ;
 	} else {
 		bounds_check_type = BPF_READ;
 	}
@@ -7230,8 +7230,7 @@ static int check_stack_range_initialized(
 		stype = &state->stack[spi].slot_type[slot % BPF_REG_SIZE];
 		if (*stype == STACK_MISC)
 			goto mark;
-		if ((*stype == STACK_ZERO) ||
-		    (*stype == STACK_INVALID && env->allow_uninit_stack)) {
+		if (*stype == STACK_ZERO) {
 			if (clobber) {
 				/* helper can write anything into the stack */
 				*stype = STACK_MISC;
@@ -8748,6 +8747,8 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 		meta->map_uid = reg->map_uid;
 		break;
 	case ARG_PTR_TO_MAP_KEY:
+		/* always mark read access */
+		meta->raw_mode = false;
 		/* bpf_map_xxx(..., map_ptr, ..., key) call:
 		 * check that [key, key + map->key_size) are within
 		 * stack limits and initialized
@@ -8763,7 +8764,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 		}
 		err = check_helper_mem_access(env, regno,
 					      meta->map_ptr->key_size, false,
-					      NULL);
+					      meta);
 		break;
 	case ARG_PTR_TO_MAP_VALUE:
 		if (type_may_be_null(arg_type) && register_is_null(reg))
-- 
2.35.3

Re: [syzbot] [bpf?] [net?] KMSAN: uninit-value in dev_map_hash_lookup_elem

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
SYZFAIL: NL802154_CMD_SET_SHORT_ADDR failed

2024/07/01 13:26:53 ignoring optional flag "sandboxArg"="0"
2024/07/01 13:26:54 parsed 1 programs
2024/07/01 13:26:55 [FATAL] failed to run ["./syz-executor" "setup" "fault" "binfmt_misc" "usb" "802154" "swap"]: exit status 67
mkdir(/syzcgroup) failed: 17
mount(binfmt_misc) failed: 16
SYZFAIL: NL802154_CMD_SET_SHORT_ADDR failed
 (errno 16: Device or resource busy)


Tested on:

commit:         e478cf26 Merge branch 'bpf-fix-a-couple-of-test-failur..
git tree:       https://linux.googlesource.com/linux/kernel/git/torvalds/linux
console output: https://syzkaller.appspot.com/x/log.txt?x=1780d2b9980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2ad6a8768920dd4b
dashboard link: https://syzkaller.appspot.com/bug?extid=80cf9d55d6fd2d6a9838
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=12b40476980000