| Message ID | 20191209132221.15328-1-ajd@linux.ibm.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 61e3acd8c693a14fc69b824cb5b08d02cb90a6e7 |
| Headers | show |
| Series | [v2] powerpc: Fix __clear_user() with KUAP enabled | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/apply_patch | success | Successfully applied on branch powerpc/merge (42159d2de18ffa66c2714d988a8c162db8b03956) |
| snowpatch_ozlabs/build-ppc64le | success | Build succeeded |
| snowpatch_ozlabs/build-ppc64be | success | Build succeeded |
| snowpatch_ozlabs/build-ppc64e | success | Build succeeded |
| snowpatch_ozlabs/build-pmac32 | success | Build succeeded |
| snowpatch_ozlabs/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 60 lines checked |
On Mon, 2019-12-09 at 13:22:21 UTC, Andrew Donnellan wrote: > The KUAP implementation adds calls in clear_user() to enable and disable > access to userspace memory. However, it doesn't add these to > __clear_user(), which is used in the ptrace regset code. > > As there's only one direct user of __clear_user(), and the time taken to > set the AMR for KUAP purposes is going to dominate the cost of a quick > access_ok(), there's not much point having a separate path. > > Rename __clear_user() to clear_user_asm(), and make __clear_user() just > call clear_user(). > > Reported-by: syzbot+f25ecf4b2982d8c7a640@syzkaller-ppc64.appspotmail.com > Reported-by: Daniel Axtens <dja@axtens.net> > Suggested-by: Michael Ellerman <mpe@ellerman.id.au> > Cc: Christophe Leroy <christophe.leroy@c-s.fr> > Cc: Russell Currey <ruscur@russell.cc> > Fixes: de78a9c42a79 ("powerpc: Add a framework for Kernel Userspace Access Protection") > Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com> Applied to powerpc fixes, thanks. https://git.kernel.org/powerpc/c/61e3acd8c693a14fc69b824cb5b08d02cb90a6e7 cheers
diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h index 15002b51ff18..c8e2bf60a5ac 100644 --- a/arch/powerpc/include/asm/uaccess.h +++ b/arch/powerpc/include/asm/uaccess.h @@ -401,7 +401,7 @@ copy_to_user_mcsafe(void __user *to, const void *from, unsigned long n) return n; } -extern unsigned long __clear_user(void __user *addr, unsigned long size); +unsigned long clear_user_asm(void __user *addr, unsigned long size); static inline unsigned long clear_user(void __user *addr, unsigned long size) { @@ -409,12 +409,17 @@ static inline unsigned long clear_user(void __user *addr, unsigned long size) might_fault(); if (likely(access_ok(addr, size))) { allow_write_to_user(addr, size); - ret = __clear_user(addr, size); + ret = clear_user_asm(addr, size); prevent_write_to_user(addr, size); } return ret; } +static inline unsigned long __clear_user(void __user *addr, unsigned long size) +{ + return clear_user(addr, size); +} + extern long strncpy_from_user(char *dst, const char __user *src, long count); extern __must_check long strnlen_user(const char __user *str, long n); diff --git a/arch/powerpc/lib/string_32.S b/arch/powerpc/lib/string_32.S index f69a6aab7bfb..39847c630470 100644 --- a/arch/powerpc/lib/string_32.S +++ b/arch/powerpc/lib/string_32.S @@ -17,7 +17,7 @@ CACHELINE_BYTES = L1_CACHE_BYTES LG_CACHELINE_BYTES = L1_CACHE_SHIFT CACHELINE_MASK = (L1_CACHE_BYTES-1) -_GLOBAL(__clear_user) +_GLOBAL(clear_user_asm) /* * Use dcbz on the complete cache lines in the destination * to set them to zero. This requires that the destination @@ -87,4 +87,4 @@ _GLOBAL(__clear_user) EX_TABLE(8b, 91b) EX_TABLE(9b, 91b) -EXPORT_SYMBOL(__clear_user) +EXPORT_SYMBOL(clear_user_asm) diff --git a/arch/powerpc/lib/string_64.S b/arch/powerpc/lib/string_64.S index 507b18b1660e..a955f5e72feb 100644 --- a/arch/powerpc/lib/string_64.S +++ b/arch/powerpc/lib/string_64.S @@ -17,7 +17,7 @@ PPC64_CACHES: .section ".text" /** - * __clear_user: - Zero a block of memory in user space, with less checking. + * clear_user_asm: - Zero a block of memory in user space, with less checking. * @to: Destination address, in user space. * @n: Number of bytes to zero. * @@ -58,7 +58,7 @@ err3; stb r0,0(r3) mr r3,r4 blr -_GLOBAL_TOC(__clear_user) +_GLOBAL_TOC(clear_user_asm) cmpdi r4,32 neg r6,r3 li r0,0 @@ -181,4 +181,4 @@ err1; dcbz 0,r3 cmpdi r4,32 blt .Lshort_clear b .Lmedium_clear -EXPORT_SYMBOL(__clear_user) +EXPORT_SYMBOL(clear_user_asm)
The KUAP implementation adds calls in clear_user() to enable and disable access to userspace memory. However, it doesn't add these to __clear_user(), which is used in the ptrace regset code. As there's only one direct user of __clear_user(), and the time taken to set the AMR for KUAP purposes is going to dominate the cost of a quick access_ok(), there's not much point having a separate path. Rename __clear_user() to clear_user_asm(), and make __clear_user() just call clear_user(). Reported-by: syzbot+f25ecf4b2982d8c7a640@syzkaller-ppc64.appspotmail.com Reported-by: Daniel Axtens <dja@axtens.net> Suggested-by: Michael Ellerman <mpe@ellerman.id.au> Cc: Christophe Leroy <christophe.leroy@c-s.fr> Cc: Russell Currey <ruscur@russell.cc> Fixes: de78a9c42a79 ("powerpc: Add a framework for Kernel Userspace Access Protection") Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com> --- v1->v2: - fix checkpatch warnings (thanks snowpatch) --- arch/powerpc/include/asm/uaccess.h | 9 +++++++-- arch/powerpc/lib/string_32.S | 4 ++-- arch/powerpc/lib/string_64.S | 6 +++--- 3 files changed, 12 insertions(+), 7 deletions(-)