2021-04-23 13:53:39

by Christophe Leroy

Subject: [PATCH] powerpc/signal32: Fix erroneous SIGSEGV on RT signal return

Return of user_read_access_begin() is tested the wrong way,
leading to a SIGSEGV when the user address is valid and likely
an Oops when the user address is bad.

Fix the test.

Fixes: 887f3ceb51cd ("powerpc/signal32: Convert do_setcontext[_tm]() to user access block")
Signed-off-by: Christophe Leroy <[email protected]>
---
arch/powerpc/kernel/signal_32.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index fc41c58f0cbb..8f05ed0da292 100644
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -967,7 +967,7 @@ static int do_setcontext(struct ucontext __user *ucp, struct pt_regs *regs, int
sigset_t set;
struct mcontext __user *mcp;

- if (user_read_access_begin(ucp, sizeof(*ucp)))
+ if (!user_read_access_begin(ucp, sizeof(*ucp)))
return -EFAULT;

unsafe_get_sigset_t(&set, &ucp->uc_sigmask, failed);
@@ -1005,7 +1005,7 @@ static int do_setcontext_tm(struct ucontext __user *ucp,
u32 cmcp;
u32 tm_cmcp;

- if (user_read_access_begin(ucp, sizeof(*ucp)))
+ if (!user_read_access_begin(ucp, sizeof(*ucp)))
return -EFAULT;

unsafe_get_sigset_t(&set, &ucp->uc_sigmask, failed);
--
2.25.0

2021-04-29 14:04:25

by Michael Ellerman

Subject: Re: [PATCH] powerpc/signal32: Fix erroneous SIGSEGV on RT signal return

On Fri, 23 Apr 2021 13:52:10 +0000 (UTC), Christophe Leroy wrote:
> Return of user_read_access_begin() is tested the wrong way,
> leading to a SIGSEGV when the user address is valid and likely
> an Oops when the user address is bad.
>
> Fix the test.

Applied to powerpc/next.

[1/1] powerpc/signal32: Fix erroneous SIGSEGV on RT signal return
https://git.kernel.org/powerpc/c/5256426247837feb8703625bda7fcfc824af04cf

cheers