zap_modalias_env() wrongly calculates size of memory block to move, so maybe cause OOB memory access issue, fixed by correcting size to memmove.
Fixes: 9b3fa47d4a76 ("kobject: fix suppressing modalias in uevents delivered over netlink") Cc: stable@vger.kernel.org Signed-off-by: Zijun Hu quic_zijuhu@quicinc.com --- lib/kobject_uevent.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c index 03b427e2707e..f153b4f9d4d9 100644 --- a/lib/kobject_uevent.c +++ b/lib/kobject_uevent.c @@ -434,7 +434,7 @@ static void zap_modalias_env(struct kobj_uevent_env *env)
if (i != env->envp_idx - 1) { memmove(env->envp[i], env->envp[i + 1], - env->buflen - len); + env->buf + env->buflen - env->envp[i + 1]);
for (j = i; j < env->envp_idx - 1; j++) env->envp[j] = env->envp[j + 1] - len;
On Fri, May 24, 2024 at 12:20:03PM +0800, Zijun Hu wrote:
zap_modalias_env() wrongly calculates size of memory block to move, so maybe cause OOB memory access issue, fixed by correcting size to memmove.
"maybe" or "does"? That's a big difference :)
Fixes: 9b3fa47d4a76 ("kobject: fix suppressing modalias in uevents delivered over netlink") Cc: stable@vger.kernel.org Signed-off-by: Zijun Hu quic_zijuhu@quicinc.com
lib/kobject_uevent.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c index 03b427e2707e..f153b4f9d4d9 100644 --- a/lib/kobject_uevent.c +++ b/lib/kobject_uevent.c @@ -434,7 +434,7 @@ static void zap_modalias_env(struct kobj_uevent_env *env) if (i != env->envp_idx - 1) { memmove(env->envp[i], env->envp[i + 1],
env->buflen - len);
env->buf + env->buflen - env->envp[i + 1]);
How is this "more correct"? Please explain it better, this logic is not obvious at all.
thanks,
greg k-h
On 5/24/2024 12:33 PM, Greg KH wrote:
On Fri, May 24, 2024 at 12:20:03PM +0800, Zijun Hu wrote:
zap_modalias_env() wrongly calculates size of memory block to move, so maybe cause OOB memory access issue, fixed by correcting size to memmove.
"maybe" or "does"? That's a big difference :)
i found this issue by reading code instead of really meeting this issue. this issue should be prone to happen if there are more than 1 other environment vars.
do you have suggestion about term to use?
Fixes: 9b3fa47d4a76 ("kobject: fix suppressing modalias in uevents delivered over netlink") Cc: stable@vger.kernel.org Signed-off-by: Zijun Hu quic_zijuhu@quicinc.com
lib/kobject_uevent.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c index 03b427e2707e..f153b4f9d4d9 100644 --- a/lib/kobject_uevent.c +++ b/lib/kobject_uevent.c @@ -434,7 +434,7 @@ static void zap_modalias_env(struct kobj_uevent_env *env) if (i != env->envp_idx - 1) { memmove(env->envp[i], env->envp[i + 1],
env->buflen - len);
env->buf + env->buflen - env->envp[i + 1]);How is this "more correct"? Please explain it better, this logic is not obvious at all.
env->envp[] contains pointers to env->buf[] with length env->buflen, we want to delete environment variable pointed by env->envp[i] with length @len as shown below.
env->buf[] |-> target block <-| 0-----------------------------------------env->buflen ^ ^ | -> @len <- | env->envp[i] env->envp[i+1]
so move "target block" forward by @len, so size of target block is env->buf + env->buflen - env->envp[i+1] instead of env->buflen -len.
do you suggest add inline comments to explain it ?
thanks,
greg k-h
On Fri, May 24, 2024 at 01:15:01PM +0800, quic_zijuhu wrote:
On 5/24/2024 12:33 PM, Greg KH wrote:
On Fri, May 24, 2024 at 12:20:03PM +0800, Zijun Hu wrote:
zap_modalias_env() wrongly calculates size of memory block to move, so maybe cause OOB memory access issue, fixed by correcting size to memmove.
"maybe" or "does"? That's a big difference :)
i found this issue by reading code instead of really meeting this issue. this issue should be prone to happen if there are more than 1 other environment vars.
But does it? Given that we have loads of memory checkers, and I haven't ever seen any report of any overrun, it would be nice to be sure.
do you have suggestion about term to use?
Some confirmation that this really is the case would be nice :)
Fixes: 9b3fa47d4a76 ("kobject: fix suppressing modalias in uevents delivered over netlink") Cc: stable@vger.kernel.org Signed-off-by: Zijun Hu quic_zijuhu@quicinc.com
lib/kobject_uevent.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c index 03b427e2707e..f153b4f9d4d9 100644 --- a/lib/kobject_uevent.c +++ b/lib/kobject_uevent.c @@ -434,7 +434,7 @@ static void zap_modalias_env(struct kobj_uevent_env *env) if (i != env->envp_idx - 1) { memmove(env->envp[i], env->envp[i + 1],
env->buflen - len);
env->buf + env->buflen - env->envp[i + 1]);How is this "more correct"? Please explain it better, this logic is not obvious at all.
env->envp[] contains pointers to env->buf[] with length env->buflen, we want to delete environment variable pointed by env->envp[i] with length @len as shown below.
env->buf[] |-> target block <-| 0-----------------------------------------env->buflen ^ ^ | -> @len <- | env->envp[i] env->envp[i+1]
so move "target block" forward by @len, so size of target block is env->buf + env->buflen - env->envp[i+1] instead of env->buflen -len.
do you suggest add inline comments to explain it ?
Yes please.
thanks,
greg k-h
On 5/24/2024 1:21 PM, Greg KH wrote:
On Fri, May 24, 2024 at 01:15:01PM +0800, quic_zijuhu wrote:
On 5/24/2024 12:33 PM, Greg KH wrote:
On Fri, May 24, 2024 at 12:20:03PM +0800, Zijun Hu wrote:
zap_modalias_env() wrongly calculates size of memory block to move, so maybe cause OOB memory access issue, fixed by correcting size to memmove.
"maybe" or "does"? That's a big difference :)
i found this issue by reading code instead of really meeting this issue. this issue should be prone to happen if there are more than 1 other environment vars.
But does it? Given that we have loads of memory checkers, and I haven't ever seen any report of any overrun, it would be nice to be sure.
yes. if @env includes env vairable MODALIAS and more than one other env vairables. then (env->buflen - len) must be greater that actual size of "target block" shown previously, so the OOB issue must happen.
do you have suggestion about term to use?
Some confirmation that this really is the case would be nice :)
Fixes: 9b3fa47d4a76 ("kobject: fix suppressing modalias in uevents delivered over netlink") Cc: stable@vger.kernel.org Signed-off-by: Zijun Hu quic_zijuhu@quicinc.com
lib/kobject_uevent.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c index 03b427e2707e..f153b4f9d4d9 100644 --- a/lib/kobject_uevent.c +++ b/lib/kobject_uevent.c @@ -434,7 +434,7 @@ static void zap_modalias_env(struct kobj_uevent_env *env) if (i != env->envp_idx - 1) { memmove(env->envp[i], env->envp[i + 1],
env->buflen - len);
env->buf + env->buflen - env->envp[i + 1]);How is this "more correct"? Please explain it better, this logic is not obvious at all.
env->envp[] contains pointers to env->buf[] with length env->buflen, we want to delete environment variable pointed by env->envp[i] with length @len as shown below.
env->buf[] |-> target block <-| 0-----------------------------------------env->buflen ^ ^ | -> @len <- | env->envp[i] env->envp[i+1]
so move "target block" forward by @len, so size of target block is env->buf + env->buflen - env->envp[i+1] instead of env->buflen -len.
do you suggest add inline comments to explain it ?
Yes please.
thanks,
greg k-h
On Fri, May 24, 2024 at 01:34:49PM +0800, quic_zijuhu wrote:
On 5/24/2024 1:21 PM, Greg KH wrote:
On Fri, May 24, 2024 at 01:15:01PM +0800, quic_zijuhu wrote:
On 5/24/2024 12:33 PM, Greg KH wrote:
On Fri, May 24, 2024 at 12:20:03PM +0800, Zijun Hu wrote:
zap_modalias_env() wrongly calculates size of memory block to move, so maybe cause OOB memory access issue, fixed by correcting size to memmove.
"maybe" or "does"? That's a big difference :)
i found this issue by reading code instead of really meeting this issue. this issue should be prone to happen if there are more than 1 other environment vars.
But does it? Given that we have loads of memory checkers, and I haven't ever seen any report of any overrun, it would be nice to be sure.
yes. if @env includes env vairable MODALIAS and more than one other env vairables. then (env->buflen - len) must be greater that actual size of "target block" shown previously, so the OOB issue must happen.
Then why are none of the tools that we have for catching out-of-bound issues triggered here? Are the tools broken or is this really just not ever happening? It would be good to figure that out...
thanks,
greg k-h
On 5/24/2024 2:56 PM, Greg KH wrote:
On Fri, May 24, 2024 at 01:34:49PM +0800, quic_zijuhu wrote:
On 5/24/2024 1:21 PM, Greg KH wrote:
On Fri, May 24, 2024 at 01:15:01PM +0800, quic_zijuhu wrote:
On 5/24/2024 12:33 PM, Greg KH wrote:
On Fri, May 24, 2024 at 12:20:03PM +0800, Zijun Hu wrote:
zap_modalias_env() wrongly calculates size of memory block to move, so maybe cause OOB memory access issue, fixed by correcting size to memmove.
"maybe" or "does"? That's a big difference :)
i found this issue by reading code instead of really meeting this issue. this issue should be prone to happen if there are more than 1 other environment vars.
But does it? Given that we have loads of memory checkers, and I haven't ever seen any report of any overrun, it would be nice to be sure.
yes. if @env includes env vairable MODALIAS and more than one other env vairables. then (env->buflen - len) must be greater that actual size of "target block" shown previously, so the OOB issue must happen.
Then why are none of the tools that we have for catching out-of-bound issues triggered here? Are the tools broken or is this really just not ever happening? It would be good to figure that out...
don't know why. perhaps, need to report our case to expert of tools.
thanks,
greg k-h
On Fri, May 24, 2024 at 05:08:06PM +0800, quic_zijuhu wrote:
On 5/24/2024 2:56 PM, Greg KH wrote:
On Fri, May 24, 2024 at 01:34:49PM +0800, quic_zijuhu wrote:
On 5/24/2024 1:21 PM, Greg KH wrote:
On Fri, May 24, 2024 at 01:15:01PM +0800, quic_zijuhu wrote:
On 5/24/2024 12:33 PM, Greg KH wrote:
On Fri, May 24, 2024 at 12:20:03PM +0800, Zijun Hu wrote: > zap_modalias_env() wrongly calculates size of memory block > to move, so maybe cause OOB memory access issue, fixed by > correcting size to memmove.
"maybe" or "does"? That's a big difference :)
i found this issue by reading code instead of really meeting this issue. this issue should be prone to happen if there are more than 1 other environment vars.
But does it? Given that we have loads of memory checkers, and I haven't ever seen any report of any overrun, it would be nice to be sure.
yes. if @env includes env vairable MODALIAS and more than one other env vairables. then (env->buflen - len) must be greater that actual size of "target block" shown previously, so the OOB issue must happen.
Then why are none of the tools that we have for catching out-of-bound issues triggered here? Are the tools broken or is this really just not ever happening? It would be good to figure that out...
don't know why. perhaps, need to report our case to expert of tools.
Try running them yourself and see!
On 5/24/2024 7:47 PM, Greg KH wrote:
On Fri, May 24, 2024 at 05:08:06PM +0800, quic_zijuhu wrote:
On 5/24/2024 2:56 PM, Greg KH wrote:
On Fri, May 24, 2024 at 01:34:49PM +0800, quic_zijuhu wrote:
On 5/24/2024 1:21 PM, Greg KH wrote:
On Fri, May 24, 2024 at 01:15:01PM +0800, quic_zijuhu wrote:
On 5/24/2024 12:33 PM, Greg KH wrote: > On Fri, May 24, 2024 at 12:20:03PM +0800, Zijun Hu wrote: >> zap_modalias_env() wrongly calculates size of memory block >> to move, so maybe cause OOB memory access issue, fixed by >> correcting size to memmove. > > "maybe" or "does"? That's a big difference :) > i found this issue by reading code instead of really meeting this issue. this issue should be prone to happen if there are more than 1 other environment vars.
But does it? Given that we have loads of memory checkers, and I haven't ever seen any report of any overrun, it would be nice to be sure.
yes. if @env includes env vairable MODALIAS and more than one other env vairables. then (env->buflen - len) must be greater that actual size of "target block" shown previously, so the OOB issue must happen.
Then why are none of the tools that we have for catching out-of-bound issues triggered here? Are the tools broken or is this really just not ever happening? It would be good to figure that out...
don't know why. perhaps, need to report our case to expert of tools.
Try running them yourself and see!
i find out the reason why the OOB issue is difficult to be observed. the reason is that MODALIAS is the last variable added by most of drivers by accident, and it skips the obvious wrong logic within zap_modalias_env().
you maybe run below command to confirm the reason. grep -l -r MODALIAS drivers/ | xargs grep add_uevent_var
On Fri, 24 May 2024, Zijun Hu wrote:
Subject: [PATCH] kobject_uevent: Fix OOB access within zap_modalias_env() zap_modalias_env() wrongly calculates size of memory block to move, so maybe cause OOB memory access issue, fixed by correcting size to memmove.
Fixes: 9b3fa47d4a76 ("kobject: fix suppressing modalias in uevents delivered over netlink") Cc: stable@vger.kernel.org Signed-off-by: Zijun Hu quic_zijuhu@quicinc.com
lib/kobject_uevent.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c index 03b427e2707e..f153b4f9d4d9 100644 --- a/lib/kobject_uevent.c +++ b/lib/kobject_uevent.c @@ -434,7 +434,7 @@ static void zap_modalias_env(struct kobj_uevent_env *env) if (i != env->envp_idx - 1) { memmove(env->envp[i], env->envp[i + 1],
env->buflen - len);
env->buf + env->buflen - env->envp[i + 1]);for (j = i; j < env->envp_idx - 1; j++) env->envp[j] = env->envp[j + 1] - len;
I notice it too.
In the debug, I find that length of "env->buflen - len" is definitely larger than "env->buf + env->buflen - env->envp[i+1". So memmove() just copy some extra '\0', and the problem will not happen when the length of env variables is much smaller than 2048. That is why the problem is difficult to be observed.
But when the length of env variables is close to 2048 or even more than 2048, the memmove will access the memory not belong to env->buf[2048].
On 6/30/2024 11:08 PM, Zhou congjie wrote:
On Fri, 24 May 2024, Zijun Hu wrote:
Subject: [PATCH] kobject_uevent: Fix OOB access within zap_modalias_env() zap_modalias_env() wrongly calculates size of memory block to move, so maybe cause OOB memory access issue, fixed by correcting size to memmove.
Fixes: 9b3fa47d4a76 ("kobject: fix suppressing modalias in uevents delivered over netlink") Cc: stable@vger.kernel.org Signed-off-by: Zijun Hu quic_zijuhu@quicinc.com
lib/kobject_uevent.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c index 03b427e2707e..f153b4f9d4d9 100644 --- a/lib/kobject_uevent.c +++ b/lib/kobject_uevent.c @@ -434,7 +434,7 @@ static void zap_modalias_env(struct kobj_uevent_env *env) if (i != env->envp_idx - 1) { memmove(env->envp[i], env->envp[i + 1],
env->buflen - len);
env->buf + env->buflen - env->envp[i + 1]);for (j = i; j < env->envp_idx - 1; j++) env->envp[j] = env->envp[j + 1] - len;
I notice it too.
In the debug, I find that length of "env->buflen - len" is definitely larger than "env->buf + env->buflen - env->envp[i+1". So memmove() just copy some extra '\0', and the problem will not happen when the length of env variables is much smaller than 2048. That is why the problem is difficult to be observed.
yes, it is a factor of why this issue is not easy to be observed
But when the length of env variables is close to 2048 or even more than 2048, the memmove will access the memory not belong to env->buf[2048].
linux-stable-mirror@lists.linaro.org
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Greg KH -
quic_zijuhu -
Zhou congjie -
Zijun Hu