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Message-ID: <ZYxEg3g8NIwcDZWM@tissot.1015granger.net> Date: Wed, 27 Dec 2023 10:36:35 -0500 From: Chuck Lever <chuck.lever@...cle.com> To: alexious@....edu.cn Cc: Trond Myklebust <trond.myklebust@...merspace.com>, Anna Schumaker <anna@...nel.org>, Jeff Layton <jlayton@...nel.org>, Neil Brown <neilb@...e.de>, Olga Kornievskaia <kolga@...app.com>, Dai Ngo <Dai.Ngo@...cle.com>, Tom Talpey <tom@...pey.com>, "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Simo Sorce <simo@...hat.com>, Steve Dickson <steved@...hat.com>, Kevin Coffman <kwc@...i.umich.edu>, linux-nfs@...r.kernel.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] SUNRPC: fix a memleak in gss_import_v2_context On Tue, Dec 26, 2023 at 05:01:05PM +0800, alexious@....edu.cn wrote: > > On Sun, Dec 24, 2023 at 04:20:33PM +0800, Zhipeng Lu wrote: > > > The ctx->mech_used.data allocated by kmemdup is not freed in neither > > > gss_import_v2_context nor it only caller radeon_driver_open_kms. > > > Thus, this patch reform the last call of gss_import_v2_context to the > > > gss_krb5_import_ctx_v2, preventing the memleak while keepping the return > > > formation. > > > > > > Fixes: 47d848077629 ("gss_krb5: handle new context format from gssd") > > > Signed-off-by: Zhipeng Lu <alexious@....edu.cn> > > > --- > > > net/sunrpc/auth_gss/gss_krb5_mech.c | 9 ++++++++- > > > 1 file changed, 8 insertions(+), 1 deletion(-) > > > > > > diff --git a/net/sunrpc/auth_gss/gss_krb5_mech.c b/net/sunrpc/auth_gss/gss_krb5_mech.c > > > index e31cfdf7eadc..1e54bd63e3f0 100644 > > > --- a/net/sunrpc/auth_gss/gss_krb5_mech.c > > > +++ b/net/sunrpc/auth_gss/gss_krb5_mech.c > > > @@ -398,6 +398,7 @@ gss_import_v2_context(const void *p, const void *end, struct krb5_ctx *ctx, > > > u64 seq_send64; > > > int keylen; > > > u32 time32; > > > + int ret; > > > > > > p = simple_get_bytes(p, end, &ctx->flags, sizeof(ctx->flags)); > > > if (IS_ERR(p)) > > > @@ -450,8 +451,14 @@ gss_import_v2_context(const void *p, const void *end, struct krb5_ctx *ctx, > > > } > > > ctx->mech_used.len = gss_kerberos_mech.gm_oid.len; > > > > > > - return gss_krb5_import_ctx_v2(ctx, gfp_mask); > > > + ret = gss_krb5_import_ctx_v2(ctx, gfp_mask); > > > + if (ret) { > > > + p = ERR_PTR(ret); > > > + goto out_free; > > > + }; > > > > > > +out_free: > > > + kfree(ctx->mech_used.data); > > > > If the caller's error flow does not invoke > > gss_krb5_delete_sec_context(), then I would expect more than just > > mech_used.data would be leaked. What if, instead, you changed > > gss_krb5_import_sec_context() like this (untested): > > > > 471 ret = gss_import_v2_context(p, end, ctx, gfp_mask); > > 472 memzero_explicit(&ctx->Ksess, sizeof(ctx->Ksess)); > > 473 if (ret) { > > - kfree(ctx); > > + gss_krb5_delete_sec_context(ctx); > > 475 return ret; > > 476 } > > > > Obviously you would need to add a forward declaration of > > gss_krb5_import_sec_context() to make this compile. The question > > is whether gss_krb5_delete_sec_context() will deal with a partially- > > initialized @ctx. > > Since the ctx is allocated just in gss_krb5_import_sec_context, > together with that all of gss_krb5_import_sec_context, gss_import_v2_context(with this patch) > and gss_krb5_import_ctx_v2 are allocation-free balanced. It seems that we don't need to > release anything else by invoking gss_krb5_delete_sec_context. > > If I miss something leaked, please let me know. I see, if gss_krb5_import_ctx_v2() fails, it releases the ciphers and hashes via out_free. So no leak there. A nicer approach would be to handle that clean up in gss_krb5_import_sec_context(): less code duplication. But you're right, it's not broken today. > > How did you find this leak, and what kind of testing was done to > > confirm the fix is safe? > > I found this memleak by static analysis. > The safety issue can't be solved by automatic tools as far as I know. > So I check patches manuelly before sending patches. Can you give some details about how you check the patches? -- Chuck Lever
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