* [PATCH][V2][Fix commit message] x86/RAS/mce_amd_inj: fix signed wrap around when decrementing index i
@ 2016-09-16 11:22 Colin King
2016-09-17 7:35 ` Borislav Petkov
0 siblings, 1 reply; 2+ messages in thread
From: Colin King @ 2016-09-16 11:22 UTC (permalink / raw)
To: Borislav Petkov, Aravind Gopalakrishnan, Yazen Ghannam, Peter Zijlstra
Cc: linux-kernel
From: Colin Ian King <colin.king@canonical.com>
Integer index i needs to be a signed int rather than unsigned to avoid
a wrap-around when decrementing in the while loop. For example, if the
debugfs_create_file fails when i is zero, the current situation will
predecrement i in the while loop, wrapping i to the maximum signed
integer and cause multiple out of bounds reads on dfs_fls[i].d as
the loop interates to zero.
Also add (int) cast to fix warning that the original fix attempted
to fix.
Fixes: 7cc4ef8ed132 ("x86/RAS/mce_amd_inj: Fix some W= warnings")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
arch/x86/ras/mce_amd_inj.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/ras/mce_amd_inj.c b/arch/x86/ras/mce_amd_inj.c
index cd318d9..cb9779a 100644
--- a/arch/x86/ras/mce_amd_inj.c
+++ b/arch/x86/ras/mce_amd_inj.c
@@ -440,7 +440,7 @@ static struct dfs_node {
static int __init init_mce_inject(void)
{
- unsigned int i;
+ int i;
u64 cap;
rdmsrl(MSR_IA32_MCG_CAP, cap);
@@ -450,7 +450,7 @@ static int __init init_mce_inject(void)
if (!dfs_inj)
return -EINVAL;
- for (i = 0; i < ARRAY_SIZE(dfs_fls); i++) {
+ for (i = 0; i < (int)ARRAY_SIZE(dfs_fls); i++) {
dfs_fls[i].d = debugfs_create_file(dfs_fls[i].name,
dfs_fls[i].perm,
dfs_inj,
--
2.9.3
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH][V2][Fix commit message] x86/RAS/mce_amd_inj: fix signed wrap around when decrementing index i
2016-09-16 11:22 [PATCH][V2][Fix commit message] x86/RAS/mce_amd_inj: fix signed wrap around when decrementing index i Colin King
@ 2016-09-17 7:35 ` Borislav Petkov
0 siblings, 0 replies; 2+ messages in thread
From: Borislav Petkov @ 2016-09-17 7:35 UTC (permalink / raw)
To: Colin King; +Cc: Yazen Ghannam, linux-kernel, Aravind Gopalakrishnan
(drop peterz from CC).
On Fri, Sep 16, 2016 at 12:22:23PM +0100, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
>
> Integer index i needs to be a signed int rather than unsigned to avoid
> a wrap-around when decrementing in the while loop. For example, if the
Damn corner cases :-\
> debugfs_create_file fails when i is zero, the current situation will
> predecrement i in the while loop, wrapping i to the maximum signed
> integer and cause multiple out of bounds reads on dfs_fls[i].d as
> the loop interates to zero.
>
> Also add (int) cast to fix warning that the original fix attempted
> to fix.
Thanks, that's a good catch!
But, can we keep the unsigned-ness of i as it is an index and do this
instead?
(Oh, and make it return ENODEV - that ENOMEM is just plain wrong most of
the time).
---
diff --git a/arch/x86/ras/mce_amd_inj.c b/arch/x86/ras/mce_amd_inj.c
index cd318d93099e..a2dafca467e6 100644
--- a/arch/x86/ras/mce_amd_inj.c
+++ b/arch/x86/ras/mce_amd_inj.c
@@ -457,8 +457,12 @@ static int __init init_mce_inject(void)
&i_mce,
dfs_fls[i].fops);
- if (!dfs_fls[i].d)
+ if (!dfs_fls[i].d) {
+ if (!i)
+ return -ENODEV;
+
goto err_dfs_add;
+ }
}
return 0;
@@ -470,7 +474,7 @@ err_dfs_add:
debugfs_remove(dfs_inj);
dfs_inj = NULL;
- return -ENOMEM;
+ return -ENODEV;
}
static void __exit exit_mce_inject(void)
--
Regards/Gruss,
Boris.
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--
^ permalink raw reply related [flat|nested] 2+ messages in thread
end of thread, other threads:[~2016-09-17 7:35 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2016-09-16 11:22 [PATCH][V2][Fix commit message] x86/RAS/mce_amd_inj: fix signed wrap around when decrementing index i Colin King
2016-09-17 7:35 ` Borislav Petkov
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.