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b=S8Veyza5n90EQD3okN0qAC+/UxS4gbEXBTUL1MzzW45keJUBajctrx5gPHZPzzWmu nvGwNNO621jnDjuEh65BDPt+Pwylr0U1A+jf1I/MPfXTmUa214d9nkErnXz+7PVVFo 9Wq3o2b+ipPue7Bb6WVyVTZWFDQucUqZuxa+9GWs= Date: Tue, 29 Oct 2024 17:45:18 -0700 From: Andrew Morton To: Marc Dionne Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Marc Dionne , Vlastimil Babka Subject: Re: [PATCH v2] tools/mm: Fix slabinfo crash when MAX_SLABS is exceeded Message-Id: <20241029174518.60fa703fc9cb304d6e69e9a0@linux-foundation.org> In-Reply-To: <20241029161341.14063-1-marc.c.dionne@gmail.com> References: <20241029161341.14063-1-marc.c.dionne@gmail.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: CC95F160008 X-Stat-Signature: gaugptbih751gcaa7ocf6ip79qabkohd X-Rspam-User: X-HE-Tag: 1730249105-750714 X-HE-Meta: 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 nuxJyzSG sCf05T52fdg6Tj6fzBrsoFRxEYSEc9QWqNgws36OpDO+GwSUXOKXQAHp8B7GDIK9CbfcyPnDdwYZaFVgU82H2IO4sGJOSv0sE/ymtAHde60dPhoPpEKnaFWzSA9A5OE2kEgm4z7qWXQq5SLMnJsXvSkfZ8G/IWBsqNIooKiQ4a9lEU0Ls/lnGNldcA7YgA+8zKuVeIx/extxNiv2+aKaf9KaQmxbBdvcRMAq7hVIp9sojCBrSGP3u1Ar99sQifHGpoZpOnQASz0VAOZNY1KpCVP9q1JLt9O3pHmnaxkyuTn2eMsvo7ydxY5+ixiHdQiBMPZkQtb0raUk/3Yu88tYoXQ0QbKarhxvZ0fjBTRuWgABW2Suz72sU5YpD6KyzSYMYdFAib/hXYyaRIXybWAa7KvbXJfM+C+GjxxpxaqdDercFo6qReyVFr2NAMqvy/dejOprN X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 29 Oct 2024 13:13:41 -0300 Marc Dionne wrote: > From: Marc Dionne > > The number of slabs can easily exceed the hard coded MAX_SLABS in the > slabinfo tool, causing it to overwrite memory and crash. > > Increase the value of MAX_SLABS, and check if that has been exceeded for > each new slab, instead of at the end when it's already too late. Also > move the check for MAX_ALIASES into the loop body. Thanks. > --- a/tools/mm/slabinfo.c > +++ b/tools/mm/slabinfo.c > @@ -21,7 +21,7 @@ > #include > #include > > -#define MAX_SLABS 500 > +#define MAX_SLABS 1000 That isn't a very large increase. > #define MAX_ALIASES 500 > #define MAX_NODES 1024 > > @@ -1240,6 +1240,8 @@ static void read_slab_dir(void) > p--; > alias->ref = strdup(p); > alias++; > + if (alias - aliasinfo > MAX_ALIASES) > + fatal("Too many aliases\n"); > break; > case DT_DIR: > if (chdir(de->d_name)) > @@ -1301,6 +1303,8 @@ static void read_slab_dir(void) > if (slab->name[0] == ':') > alias_targets++; > slab++; > + if (slab - slabinfo > MAX_SLABS) > + fatal("Too many slabs\n"); > break; This could be improved - if the number of slabs is exactly equal to MAX_SLABS we'll unnecessarily report an error. Wouldn't this alteration be better? --- a/tools/mm/slabinfo.c~tools-mm-fix-slabinfo-crash-when-max_slabs-is-exceeded-fix +++ a/tools/mm/slabinfo.c @@ -1228,6 +1228,8 @@ static void read_slab_dir(void) continue; switch (de->d_type) { case DT_LNK: + if (alias - aliasinfo >= MAX_ALIASES) + fatal("Too many aliases\n"); alias->name = strdup(de->d_name); count = readlink(de->d_name, buffer, sizeof(buffer)-1); @@ -1240,10 +1242,10 @@ static void read_slab_dir(void) p--; alias->ref = strdup(p); alias++; - if (alias - aliasinfo > MAX_ALIASES) - fatal("Too many aliases\n"); break; case DT_DIR: + if (slab - slabinfo >= MAX_SLABS) + fatal("Too many slabs\n"); if (chdir(de->d_name)) fatal("Unable to access slab %s\n", slab->name); slab->name = strdup(de->d_name); @@ -1305,8 +1307,6 @@ static void read_slab_dir(void) if (slab->name[0] == ':') alias_targets++; slab++; - if (slab - slabinfo > MAX_SLABS) - fatal("Too many slabs\n"); break; default : fatal("Unknown file type %lx\n", de->d_type); _