| Message ID | 1508831057-64195-1-git-send-email-puck.chen@hisilicon.com |
|---|---|
| State | New |
| Headers | show |
| Series | [RFC] random: fix syzkaller fuzzer test int overflow | expand |
On Tue, Oct 24, 2017 at 03:44:17PM +0800, Chen Feng wrote: > [pid:11940,cpu6,syz-executor][flp_ioctl]cmd[0x1] > Restart is not permit > ================================================================= > UBSAN: Undefined behaviour in > kernel/linux-4.4/drivers/char/random.c:676:19 > signed integer overflow: > 2147483645 + 268435455 cannot be represented in type 'int' > CPU: 4 PID: 11941 Comm: syz-executor Not tainted 4.4.76+ #2 Does this also happen on 4.14-rc6? > TGID: 11928 Comm: syz-executor > Hardware name: hi3660 (DT) > Call trace: > [<ffffffa661090378>] dump_backtrace+0x0/0x314 > [<ffffffa66109077c>] show_stack+0x1c/0x24 > [<ffffffa66180cc54>] dump_stack+0xdc/0x130 > [<ffffffa6618833d0>] ubsan_epilogue+0x18/0x6c > [<ffffffa661883c5c>] handle_overflow+0x180/0x1d4 > [<ffffffa661883cdc>] __ubsan_handle_add_overflow+0x2c/0x34 > [<ffffffa661ab75a0>] credit_entropy_bits+0x358/0x9a8 > [<ffffffa661ab85bc>] random_ioctl+0x338/0x384 > [<ffffffa661399c74>] do_vfs_ioctl+0x60c/0xa4c > [<ffffffa66139a150>] SyS_ioctl+0x9c/0xc0 > [<ffffffa6610838b0>] el0_svc_naked+0x24/0x28 > ================================================================= > > Signed-off-by: Chen Feng <puck.chen@hisilicon.com> > Signed-off-by: Yukun Zhao <zhaoyukun@huawei.com> > --- > drivers/char/random.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/drivers/char/random.c b/drivers/char/random.c > index 1ef2640..6f2bd6a 100644 > --- a/drivers/char/random.c > +++ b/drivers/char/random.c > @@ -699,6 +699,11 @@ static void credit_entropy_bits(struct entropy_store *r, int nbits) > if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig) > goto retry; > > + if (INT_MAX - nbits < r->entropy_total) { > + WARN_ON(1); Why WARN_ON()? What is that going to help with? thanks, greg k-h
On 2017/10/24 17:09, Greg KH wrote: > On Tue, Oct 24, 2017 at 03:44:17PM +0800, Chen Feng wrote: >> [pid:11940,cpu6,syz-executor][flp_ioctl]cmd[0x1] >> Restart is not permit >> ================================================================= >> UBSAN: Undefined behaviour in >> kernel/linux-4.4/drivers/char/random.c:676:19 >> signed integer overflow: >> 2147483645 + 268435455 cannot be represented in type 'int' >> CPU: 4 PID: 11941 Comm: syz-executor Not tainted 4.4.76+ #2 > > Does this also happen on 4.14-rc6? No, mainline also has this issue. > >> TGID: 11928 Comm: syz-executor >> Hardware name: hi3660 (DT) >> Call trace: >> [<ffffffa661090378>] dump_backtrace+0x0/0x314 >> [<ffffffa66109077c>] show_stack+0x1c/0x24 >> [<ffffffa66180cc54>] dump_stack+0xdc/0x130 >> [<ffffffa6618833d0>] ubsan_epilogue+0x18/0x6c >> [<ffffffa661883c5c>] handle_overflow+0x180/0x1d4 >> [<ffffffa661883cdc>] __ubsan_handle_add_overflow+0x2c/0x34 >> [<ffffffa661ab75a0>] credit_entropy_bits+0x358/0x9a8 >> [<ffffffa661ab85bc>] random_ioctl+0x338/0x384 >> [<ffffffa661399c74>] do_vfs_ioctl+0x60c/0xa4c >> [<ffffffa66139a150>] SyS_ioctl+0x9c/0xc0 >> [<ffffffa6610838b0>] el0_svc_naked+0x24/0x28 >> ================================================================= >> >> Signed-off-by: Chen Feng <puck.chen@hisilicon.com> >> Signed-off-by: Yukun Zhao <zhaoyukun@huawei.com> >> --- >> drivers/char/random.c | 5 +++++ >> 1 file changed, 5 insertions(+) >> >> diff --git a/drivers/char/random.c b/drivers/char/random.c >> index 1ef2640..6f2bd6a 100644 >> --- a/drivers/char/random.c >> +++ b/drivers/char/random.c >> @@ -699,6 +699,11 @@ static void credit_entropy_bits(struct entropy_store *r, int nbits) >> if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig) >> goto retry; >> >> + if (INT_MAX - nbits < r->entropy_total) { >> + WARN_ON(1); > > Why WARN_ON()? What is that going to help with? Actually, I am not familiar with the random module.... This patch is RFC to see if some one has better idea. -feng > > thanks, > > greg k-h > > . >
On Tue, Oct 24, 2017 at 05:24:01PM +0800, Chen Feng wrote: > > > On 2017/10/24 17:09, Greg KH wrote: > > On Tue, Oct 24, 2017 at 03:44:17PM +0800, Chen Feng wrote: > >> [pid:11940,cpu6,syz-executor][flp_ioctl]cmd[0x1] > >> Restart is not permit > >> ================================================================= > >> UBSAN: Undefined behaviour in > >> kernel/linux-4.4/drivers/char/random.c:676:19 > >> signed integer overflow: > >> 2147483645 + 268435455 cannot be represented in type 'int' > >> CPU: 4 PID: 11941 Comm: syz-executor Not tainted 4.4.76+ #2 > > > > Does this also happen on 4.14-rc6? > > No, mainline also has this issue. > > > >> TGID: 11928 Comm: syz-executor > >> Hardware name: hi3660 (DT) > >> Call trace: > >> [<ffffffa661090378>] dump_backtrace+0x0/0x314 > >> [<ffffffa66109077c>] show_stack+0x1c/0x24 > >> [<ffffffa66180cc54>] dump_stack+0xdc/0x130 > >> [<ffffffa6618833d0>] ubsan_epilogue+0x18/0x6c > >> [<ffffffa661883c5c>] handle_overflow+0x180/0x1d4 > >> [<ffffffa661883cdc>] __ubsan_handle_add_overflow+0x2c/0x34 > >> [<ffffffa661ab75a0>] credit_entropy_bits+0x358/0x9a8 > >> [<ffffffa661ab85bc>] random_ioctl+0x338/0x384 > >> [<ffffffa661399c74>] do_vfs_ioctl+0x60c/0xa4c > >> [<ffffffa66139a150>] SyS_ioctl+0x9c/0xc0 > >> [<ffffffa6610838b0>] el0_svc_naked+0x24/0x28 > >> ================================================================= > >> > >> Signed-off-by: Chen Feng <puck.chen@hisilicon.com> > >> Signed-off-by: Yukun Zhao <zhaoyukun@huawei.com> > >> --- > >> drivers/char/random.c | 5 +++++ > >> 1 file changed, 5 insertions(+) > >> > >> diff --git a/drivers/char/random.c b/drivers/char/random.c > >> index 1ef2640..6f2bd6a 100644 > >> --- a/drivers/char/random.c > >> +++ b/drivers/char/random.c > >> @@ -699,6 +699,11 @@ static void credit_entropy_bits(struct entropy_store *r, int nbits) > >> if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig) > >> goto retry; > >> > >> + if (INT_MAX - nbits < r->entropy_total) { > >> + WARN_ON(1); > > > > Why WARN_ON()? What is that going to help with? > Actually, I am not familiar with the random module.... > > This patch is RFC to see if some one has better idea. Well, not spamming the kernel log for something that userspace can trigger is a good start to modifying your patch :) thanks, greg k-h
On Tue, Oct 24, 2017 at 11:09:27AM +0200, Greg KH wrote: > On Tue, Oct 24, 2017 at 03:44:17PM +0800, Chen Feng wrote: > > [pid:11940,cpu6,syz-executor][flp_ioctl]cmd[0x1] > > Restart is not permit > > ================================================================= > > UBSAN: Undefined behaviour in > > kernel/linux-4.4/drivers/char/random.c:676:19 > > signed integer overflow: > > 2147483645 + 268435455 cannot be represented in type 'int' > > CPU: 4 PID: 11941 Comm: syz-executor Not tainted 4.4.76+ #2 > > Does this also happen on 4.14-rc6? No. It was fixed in 4.8, by commit 86a574de4590: "random: strengthen input validation for RNDADDTOENTCNT". - Ted
Hi Ted, On 2017/10/24 18:25, Theodore Ts'o wrote: > On Tue, Oct 24, 2017 at 11:09:27AM +0200, Greg KH wrote: >> On Tue, Oct 24, 2017 at 03:44:17PM +0800, Chen Feng wrote: >>> [pid:11940,cpu6,syz-executor][flp_ioctl]cmd[0x1] >>> Restart is not permit >>> ================================================================= >>> UBSAN: Undefined behaviour in >>> kernel/linux-4.4/drivers/char/random.c:676:19 >>> signed integer overflow: >>> 2147483645 + 268435455 cannot be represented in type 'int' >>> CPU: 4 PID: 11941 Comm: syz-executor Not tainted 4.4.76+ #2 >> >> Does this also happen on 4.14-rc6? > > No. It was fixed in 4.8, by commit 86a574de4590: "random: strengthen > input validation for RNDADDTOENTCNT". I see my kernel has already merged this patch. So I don't think this patch can resolve the issue above. -feng > > - Ted > > . >
On Wed, Oct 25, 2017 at 02:30:56PM +0800, Chen Feng wrote: > Hi Ted, > > On 2017/10/24 18:25, Theodore Ts'o wrote: > > On Tue, Oct 24, 2017 at 11:09:27AM +0200, Greg KH wrote: > >> On Tue, Oct 24, 2017 at 03:44:17PM +0800, Chen Feng wrote: > >>> [pid:11940,cpu6,syz-executor][flp_ioctl]cmd[0x1] > >>> Restart is not permit > >>> ================================================================= > >>> UBSAN: Undefined behaviour in > >>> kernel/linux-4.4/drivers/char/random.c:676:19 > >>> signed integer overflow: > >>> 2147483645 + 268435455 cannot be represented in type 'int' > >>> CPU: 4 PID: 11941 Comm: syz-executor Not tainted 4.4.76+ #2 > >> > >> Does this also happen on 4.14-rc6? > > > > No. It was fixed in 4.8, by commit 86a574de4590: "random: strengthen > > input validation for RNDADDTOENTCNT". > > > I see my kernel has already merged this patch. So I don't think this patch > can resolve the issue above. Do you have a reproducer for this issue that we can use to test? thanks, greg k-h
On 2017/10/25 14:56, Greg KH wrote: > On Wed, Oct 25, 2017 at 02:30:56PM +0800, Chen Feng wrote: >> Hi Ted, >> >> On 2017/10/24 18:25, Theodore Ts'o wrote: >>> On Tue, Oct 24, 2017 at 11:09:27AM +0200, Greg KH wrote: >>>> On Tue, Oct 24, 2017 at 03:44:17PM +0800, Chen Feng wrote: >>>>> [pid:11940,cpu6,syz-executor][flp_ioctl]cmd[0x1] >>>>> Restart is not permit >>>>> ================================================================= >>>>> UBSAN: Undefined behaviour in >>>>> kernel/linux-4.4/drivers/char/random.c:676:19 >>>>> signed integer overflow: >>>>> 2147483645 + 268435455 cannot be represented in type 'int' >>>>> CPU: 4 PID: 11941 Comm: syz-executor Not tainted 4.4.76+ #2 >>>> >>>> Does this also happen on 4.14-rc6? >>> >>> No. It was fixed in 4.8, by commit 86a574de4590: "random: strengthen >>> input validation for RNDADDTOENTCNT". >> >> >> I see my kernel has already merged this patch. So I don't think this patch >> can resolve the issue above. > > Do you have a reproducer for this issue that we can use to test? > It's hard to reproduce, we found this on stress test with syzkaller test. r3 = syz_open_dev$urandom(&(0x7f000000a000)="2f6465762f7572616e646f6d00", 0x0, 0x0) syz_open_dev$urandom(&(0x7f000000a000)="2f6465762f7572616e646f6d00", 0x0, 0x0) r3 = syz_open_dev$urandom(&(0x7f000000a000)="2f6465762f7572616e646f6d00", 0x0, 0x0) syz_open_dev$urandom(&(0x7f000000a000)="2f6465762f7572616e646f6d00", 0x0, 0x0) syz_open_dev$random(&(0x7f0000005000-0xc)="2f6465762f72616e646f6d00", 0x0, 0x10100) r3 = syz_open_dev$urandom(&(0x7f000000a000)="2f6465762f7572616e646f6d00", 0x0, 0x0) r3 = syz_open_dev$urandom(&(0x7f000000a000)="2f6465762f7572616e646f6d00", 0x0, 0x0) r3 = syz_open_dev$urandom(&(0x7f000000a000)="2f6465762f7572616e646f6d00", 0x0, 0x0) r3 = syz_open_dev$urandom(&(0x7f000000a000)="2f6465762f7572616e646f6d00", 0x0, 0x0) r3 = syz_open_dev$urandom(&(0x7f000000a000)="2f6465762f7572616e646f6d00", 0x0, 0x0) r3 = syz_open_dev$urandom(&(0x7f000000a000)="2f6465762f7572616e646f6d00", 0x0, 0x0) r3 = syz_open_dev$urandom(&(0x7f000000a000)="2f6465762f7572616e646f6d00", 0x0, 0x0) r3 = syz_open_dev$urandom(&(0x7f000000a000)="2f6465762f7572616e646f6d00", 0x0, 0x0) r3 = syz_open_dev$urandom(&(0x7f000000a000)="2f6465762f7572616e646f6d00", 0x0, 0x0) r3 = syz_open_dev$urandom(&(0x7f000000a000)="2f6465762f7572616e646f6d00", 0x0, 0x0) UBSAN: Undefined behaviour in kernel/linux-4.4/drivers/char/random.c:676:19 [<ffffffa661ab85bc>] random_ioctl+0x338/0x384 git log --oneline drivers/char/random.c 3991576 random: properly align get_random_int_hash 5f87c47 Merge branch 'linux-linaro-lsk-v4.4' into linux-linaro-lsk-v4.4-android f48dd2d random: add interrupt callback to VMBus IRQ handler 529025b random: print a warning for the first ten uninitialized random users f41fc0b random: initialize the non-blocking pool via add_hwgenerator_randomness() fdd8543 Merge branch 'linux-linaro-lsk-v4.4' into linux-linaro-lsk-v4.4-android 93f84c8 random: strengthen input validation for RNDADDTOENTCNT 06bfe14 FROMLIST: drivers: char: random: add get_random_long() c271950 random: Remove kernel blocking API 205a525 random: Add callback API for random pool readiness 16b369a random: Blocking API for accessing nonblocking_pool 1d9de44 random: Wake up all getrandom(2) callers when pool is ready 19acc77 random: Fix fast_mix() function > thanks, > > greg k-h > > . >
Other people who have sent me fuzzer test reproducers are able to
reproduce syzkaller logs into a simple C program. Can you explain to
me what the heck:
> r3 = syz_open_dev$urandom(&(0x7f000000a000)="2f6465762f7572616e646f6d00", 0x0, 0x0)
means?
- Ted
On 2017/10/25 16:49, Theodore Ts'o wrote: > Other people who have sent me fuzzer test reproducers are able to > reproduce syzkaller logs into a simple C program. Can you explain to > me what the heck: > >> r3 = syz_open_dev$urandom(&(0x7f000000a000)="2f6465762f7572616e646f6d00", 0x0, 0x0) > > means? Take a look at this: https://github.com/google/syzkaller/blob/master/sys/linux/random.txt > > - Ted > >
On Thu, Oct 26, 2017 at 04:25:15PM +0800, Chen Feng wrote: > > > On 2017/10/25 16:49, Theodore Ts'o wrote: > > Other people who have sent me fuzzer test reproducers are able to > > reproduce syzkaller logs into a simple C program. Can you explain to > > me what the heck: > > > >> r3 = syz_open_dev$urandom(&(0x7f000000a000)="2f6465762f7572616e646f6d00", 0x0, 0x0) > > > > means? > > Take a look at this: > > https://github.com/google/syzkaller/blob/master/sys/linux/random.txt Sorry, this *still* looks like gobbledygook. What ioctls are you executing, and with what arguments? *Please*, give me a C program I can compile. -Ted
Hi ted, On 2017/10/26 23:04, Theodore Ts'o wrote: > On Thu, Oct 26, 2017 at 04:25:15PM +0800, Chen Feng wrote: >> >> >> On 2017/10/25 16:49, Theodore Ts'o wrote: >>> Other people who have sent me fuzzer test reproducers are able to >>> reproduce syzkaller logs into a simple C program. Can you explain to >>> me what the heck: >>> >>>> r3 = syz_open_dev$urandom(&(0x7f000000a000)="2f6465762f7572616e646f6d00", 0x0, 0x0) >>> >>> means? >> >> Take a look at this: >> >> https://github.com/google/syzkaller/blob/master/sys/linux/random.txt > > Sorry, this *still* looks like gobbledygook. > > What ioctls are you executing, and with what arguments? > > *Please*, give me a C program I can compile. I checked the ioctl. What's the purpose of RNDADDTOENTCNT ioctl to userspace? We need to checked the user-input at credit_entropy_bits_safe. + if (INT_MAX - nbits < r->entropy_total) + return -EINVAL; + The test-code below: void *random_ioctl_test(void *args) { int fd = -1; int ret = -1; int test_arg = 0x7fffffff; fd = open("dev/urandom", 0x0, 0x0); if (fd < 0) { printf("open dev/urandom failed!\n"); return NULL; } ret = ioctl(fd, 0x40045201, &test_arg); printf("random_ioctl ret=%d\n", ret); close(fd); return NULL; } int main(int argc, char *argv[]) { int ret, i; pthread_t thread[100]; for (i = 0; i < 100; i++) { ret = pthread_create(&thread[i], NULL, random_ioctl_test, &i); if (ret) { printf("create thread %d fail with ret=%d\n", i, ret); return -1; } } for (i = 0; i < 100; i++) { pthread_join(thread[i], NULL); } return 0; } > > -Ted > > . >
On Sat, Oct 28, 2017 at 11:22:00AM +0800, Chen Feng wrote: > > I checked the ioctl. What's the purpose of RNDADDTOENTCNT ioctl to > userspace? It's a legacy ioctl which is probably not used anywhere; it's been replaced by RNDADDENTROPY. It previously allows root to bump the entropy estimate, but the right way to do this by rngd is to atomically add entropy to the pool land and bump the entropy estimate at the same time. The UBSAN is harmless. The ioctl requires root, and the entropy_total field, which is involved in the UBSAN, is only used in the first few seconds of boot, to determine when the entropy pool has been initialized. In general on desktop and servers this happens before userspace has a chance to run. In any case, here's a fix for this. - Ted commit 6f7034d0c52e21f30002b95126b6b98e4618dc57 Author: Theodore Ts'o <tytso@mit.edu> Date: Sun Oct 29 14:17:26 2017 -0400 random: use a tighter cap in credit_entropy_bits_safe() This fixes a harmless UBSAN where root could potentially end up causing an overflow while bumping the entropy_total field (which is ignored once the entropy pool has been initialized, and this generally is completed during the boot sequence). This is marginal for the stable kernel series, but it's a really trivial patch, and it UBSAN warning that might cause security folks to get overly excited for no reason. Signed-off-by: Theodore Ts'o <tytso@mit.edu> Cc: stable@vger.kernel.org diff --git a/drivers/char/random.c b/drivers/char/random.c index 8ad92707e45f..ae8a2f829890 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -733,7 +733,7 @@ static void credit_entropy_bits(struct entropy_store *r, int nbits) static int credit_entropy_bits_safe(struct entropy_store *r, int nbits) { - const int nbits_max = (int)(~0U >> (ENTROPY_SHIFT + 1)); + const int nbits_max = r->poolinfo->poolwords * 32; if (nbits < 0) return -EINVAL;
On Sun, Oct 29, 2017 at 02:25:29PM -0400, Theodore Ts'o wrote: > On Sat, Oct 28, 2017 at 11:22:00AM +0800, Chen Feng wrote: > > > > I checked the ioctl. What's the purpose of RNDADDTOENTCNT ioctl to > > userspace? > > It's a legacy ioctl which is probably not used anywhere; it's been > replaced by RNDADDENTROPY. It previously allows root to bump the > entropy estimate, but the right way to do this by rngd is to > atomically add entropy to the pool land and bump the entropy estimate > at the same time. > > The UBSAN is harmless. The ioctl requires root, and the entropy_total > field, which is involved in the UBSAN, is only used in the first few > seconds of boot, to determine when the entropy pool has been > initialized. In general on desktop and servers this happens before > userspace has a chance to run. > > In any case, here's a fix for this. > > - Ted > > commit 6f7034d0c52e21f30002b95126b6b98e4618dc57 > Author: Theodore Ts'o <tytso@mit.edu> > Date: Sun Oct 29 14:17:26 2017 -0400 > > random: use a tighter cap in credit_entropy_bits_safe() > > This fixes a harmless UBSAN where root could potentially end up > causing an overflow while bumping the entropy_total field (which is > ignored once the entropy pool has been initialized, and this generally > is completed during the boot sequence). > > This is marginal for the stable kernel series, but it's a really > trivial patch, and it UBSAN warning that might cause security folks to > get overly excited for no reason. > > Signed-off-by: Theodore Ts'o <tytso@mit.edu> > Cc: stable@vger.kernel.org No "Reported-by:"? thanks, greg k-h
On Mon, Oct 30, 2017 at 08:39:56AM +0100, Greg KH wrote: > > No "Reported-by:"? Good point, fixed in my tree. - Ted
================================================================= UBSAN: Undefined behaviour in kernel/linux-4.4/drivers/char/random.c:676:19 signed integer overflow: 2147483645 + 268435455 cannot be represented in type 'int' CPU: 4 PID: 11941 Comm: syz-executor Not tainted 4.4.76+ #2 TGID: 11928 Comm: syz-executor Hardware name: hi3660 (DT) Call trace: [<ffffffa661090378>] dump_backtrace+0x0/0x314 [<ffffffa66109077c>] show_stack+0x1c/0x24 [<ffffffa66180cc54>] dump_stack+0xdc/0x130 [<ffffffa6618833d0>] ubsan_epilogue+0x18/0x6c [<ffffffa661883c5c>] handle_overflow+0x180/0x1d4 [<ffffffa661883cdc>] __ubsan_handle_add_overflow+0x2c/0x34 [<ffffffa661ab75a0>] credit_entropy_bits+0x358/0x9a8 [<ffffffa661ab85bc>] random_ioctl+0x338/0x384 [<ffffffa661399c74>] do_vfs_ioctl+0x60c/0xa4c [<ffffffa66139a150>] SyS_ioctl+0x9c/0xc0 [<ffffffa6610838b0>] el0_svc_naked+0x24/0x28 ================================================================= Signed-off-by: Chen Feng <puck.chen@hisilicon.com> Signed-off-by: Yukun Zhao <zhaoyukun@huawei.com> --- drivers/char/random.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/char/random.c b/drivers/char/random.c index 1ef2640..6f2bd6a 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -699,6 +699,11 @@ static void credit_entropy_bits(struct entropy_store *r, int nbits) if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig) goto retry; + if (INT_MAX - nbits < r->entropy_total) { + WARN_ON(1); + return; + } + r->entropy_total += nbits; if (!r->initialized && r->entropy_total > 128) { r->initialized = 1;