| Message ID | 20210111194738.132139-1-sdf@google.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | [bpf] bpf: don't leak memory in bpf getsockopt when optlen == 0 | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | success | Link |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Clearly marked for bpf |
| netdev/subject_prefix | success | Link |
| netdev/cc_maintainers | warning | 5 maintainers not CCed: yhs@fb.com kpsingh@kernel.org andrii@kernel.org songliubraving@fb.com john.fastabend@gmail.com |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 4 this patch: 4 |
| netdev/kdoc | success | Errors and warnings before: 3 this patch: 3 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | warning | CHECK: Comparison to NULL could be written "!kernel_optval" |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 4 this patch: 4 |
| netdev/header_inline | success | Link |
| netdev/stable | success | Stable not CCed |
On Mon, Jan 11, 2021 at 11:47:38AM -0800, Stanislav Fomichev wrote: > optlen == 0 indicates that the kernel should ignore BPF buffer > and use the original one from the user. We, however, forget > to free the temporary buffer that we've allocated for BPF. > > Reported-by: Martin KaFai Lau <kafai@fb.com> > Fixes: d8fe449a9c51 ("bpf: Don't return EINVAL from {get,set}sockopt when optlen > PAGE_SIZE") > Signed-off-by: Stanislav Fomichev <sdf@google.com> > --- > kernel/bpf/cgroup.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c > index 6ec088a96302..09179ab72c03 100644 > --- a/kernel/bpf/cgroup.c > +++ b/kernel/bpf/cgroup.c > @@ -1395,7 +1395,7 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level, > } > > out: > - if (ret) > + if (*kernel_optval == NULL) It seems fragile to depend on the caller to init *kernel_optval to NULL. How about something like: diff --git i/kernel/bpf/cgroup.c w/kernel/bpf/cgroup.c index 6ec088a96302..8d94c004e781 100644 --- i/kernel/bpf/cgroup.c +++ w/kernel/bpf/cgroup.c @@ -1358,7 +1358,7 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level, if (copy_from_user(ctx.optval, optval, min(*optlen, max_optlen)) != 0) { ret = -EFAULT; - goto out; + goto err_out; } lock_sock(sk); @@ -1368,7 +1368,7 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level, if (!ret) { ret = -EPERM; - goto out; + goto err_out; } if (ctx.optlen == -1) { @@ -1379,7 +1379,6 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level, ret = -EFAULT; } else { /* optlen within bounds, run kernel handler */ - ret = 0; /* export any potential modifications */ *level = ctx.level; @@ -1391,12 +1390,15 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level, if (ctx.optlen != 0) { *optlen = ctx.optlen; *kernel_optval = ctx.optval; + } else { + sockopt_free_buf(&ctx); } + + return 0; } -out: - if (ret) - sockopt_free_buf(&ctx); +err_out: + sockopt_free_buf(&ctx); return ret; }
On Mon, Jan 11, 2021 at 2:32 PM Martin KaFai Lau <kafai@fb.com> wrote: > > On Mon, Jan 11, 2021 at 11:47:38AM -0800, Stanislav Fomichev wrote: > > optlen == 0 indicates that the kernel should ignore BPF buffer > > and use the original one from the user. We, however, forget > > to free the temporary buffer that we've allocated for BPF. > > > > Reported-by: Martin KaFai Lau <kafai@fb.com> > > Fixes: d8fe449a9c51 ("bpf: Don't return EINVAL from {get,set}sockopt when optlen > PAGE_SIZE") > > Signed-off-by: Stanislav Fomichev <sdf@google.com> > > --- > > kernel/bpf/cgroup.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c > > index 6ec088a96302..09179ab72c03 100644 > > --- a/kernel/bpf/cgroup.c > > +++ b/kernel/bpf/cgroup.c > > @@ -1395,7 +1395,7 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level, > > } > > > > out: > > - if (ret) > > + if (*kernel_optval == NULL) > It seems fragile to depend on the caller to init *kernel_optval to NULL. We can manually reset it to NULL when we enter __cgroup_bpf_run_filter_setsockopt, I didn't bother since there is only one existing caller. But you patch also LGTM, I don't really have a preference. > How about something like: > > diff --git i/kernel/bpf/cgroup.c w/kernel/bpf/cgroup.c > index 6ec088a96302..8d94c004e781 100644 > --- i/kernel/bpf/cgroup.c > +++ w/kernel/bpf/cgroup.c > @@ -1358,7 +1358,7 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level, > > if (copy_from_user(ctx.optval, optval, min(*optlen, max_optlen)) != 0) { > ret = -EFAULT; > - goto out; > + goto err_out; > } > > lock_sock(sk); > @@ -1368,7 +1368,7 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level, > > if (!ret) { > ret = -EPERM; > - goto out; > + goto err_out; > } > > if (ctx.optlen == -1) { > @@ -1379,7 +1379,6 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level, > ret = -EFAULT; > } else { > /* optlen within bounds, run kernel handler */ > - ret = 0; > > /* export any potential modifications */ > *level = ctx.level; > @@ -1391,12 +1390,15 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level, > if (ctx.optlen != 0) { > *optlen = ctx.optlen; > *kernel_optval = ctx.optval; > + } else { > + sockopt_free_buf(&ctx); > } > + > + return 0; > } > > -out: > - if (ret) > - sockopt_free_buf(&ctx); > +err_out: > + sockopt_free_buf(&ctx); > return ret; > }
On Mon, Jan 11, 2021 at 02:38:02PM -0800, Stanislav Fomichev wrote: > On Mon, Jan 11, 2021 at 2:32 PM Martin KaFai Lau <kafai@fb.com> wrote: > > > > On Mon, Jan 11, 2021 at 11:47:38AM -0800, Stanislav Fomichev wrote: > > > optlen == 0 indicates that the kernel should ignore BPF buffer > > > and use the original one from the user. We, however, forget > > > to free the temporary buffer that we've allocated for BPF. > > > > > > Reported-by: Martin KaFai Lau <kafai@fb.com> > > > Fixes: d8fe449a9c51 ("bpf: Don't return EINVAL from {get,set}sockopt when optlen > PAGE_SIZE") > > > Signed-off-by: Stanislav Fomichev <sdf@google.com> > > > --- > > > kernel/bpf/cgroup.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c > > > index 6ec088a96302..09179ab72c03 100644 > > > --- a/kernel/bpf/cgroup.c > > > +++ b/kernel/bpf/cgroup.c > > > @@ -1395,7 +1395,7 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level, > > > } > > > > > > out: > > > - if (ret) > > > + if (*kernel_optval == NULL) > > It seems fragile to depend on the caller to init *kernel_optval to NULL. > We can manually reset it to NULL when we enter > __cgroup_bpf_run_filter_setsockopt, It feels weird to reset the caller value at the beginning while this is not intended to be an _init() like function, so I avoided it. but yeah, I am fine on this way also and won't oppose it strongly ;) > I didn't bother since there is only one existing caller. > > But you patch also LGTM, I don't really have a preference. > > > How about something like: > > > > diff --git i/kernel/bpf/cgroup.c w/kernel/bpf/cgroup.c > > index 6ec088a96302..8d94c004e781 100644 > > --- i/kernel/bpf/cgroup.c > > +++ w/kernel/bpf/cgroup.c > > @@ -1358,7 +1358,7 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level, > > > > if (copy_from_user(ctx.optval, optval, min(*optlen, max_optlen)) != 0) { > > ret = -EFAULT; > > - goto out; > > + goto err_out; > > } > > > > lock_sock(sk); > > @@ -1368,7 +1368,7 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level, > > > > if (!ret) { > > ret = -EPERM; > > - goto out; > > + goto err_out; > > } > > > > if (ctx.optlen == -1) { > > @@ -1379,7 +1379,6 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level, > > ret = -EFAULT; > > } else { > > /* optlen within bounds, run kernel handler */ > > - ret = 0; > > > > /* export any potential modifications */ > > *level = ctx.level; > > @@ -1391,12 +1390,15 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level, > > if (ctx.optlen != 0) { > > *optlen = ctx.optlen; > > *kernel_optval = ctx.optval; > > + } else { > > + sockopt_free_buf(&ctx); > > } > > + > > + return 0; > > } > > > > -out: > > - if (ret) > > - sockopt_free_buf(&ctx); > > +err_out: > > + sockopt_free_buf(&ctx); > > return ret; > > }
diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c index 6ec088a96302..09179ab72c03 100644 --- a/kernel/bpf/cgroup.c +++ b/kernel/bpf/cgroup.c @@ -1395,7 +1395,7 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level, } out: - if (ret) + if (*kernel_optval == NULL) sockopt_free_buf(&ctx); return ret; }
optlen == 0 indicates that the kernel should ignore BPF buffer and use the original one from the user. We, however, forget to free the temporary buffer that we've allocated for BPF. Reported-by: Martin KaFai Lau <kafai@fb.com> Fixes: d8fe449a9c51 ("bpf: Don't return EINVAL from {get,set}sockopt when optlen > PAGE_SIZE") Signed-off-by: Stanislav Fomichev <sdf@google.com> --- kernel/bpf/cgroup.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)