On Tue, 29 Oct 2024 13:13:41 -0300 Marc Dionne <marc.c.dionne@xxxxxxxxx> wrote:
> From: Marc Dionne <marc.dionne@xxxxxxxxxxxx>
>
> 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 <regex.h>
> #include <errno.h>
>
> -#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);
_
