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| author | Michael Ellerman <mpe@ellerman.id.au> | 2023-11-21 10:54:36 +1100 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2023-11-27 22:05:14 +1100 |
| commit | df99da19c6c24ab65052ae1bc0904f99069478d9 (patch) | |
| tree | ce88362958cb0e42adc525f7666b4278f6c2e1ba /arch/powerpc/lib | |
| parent | 45b1ba7e5d1f6881050d558baf9bc74a2ae13930 (diff) | |
powerpc/lib: Avoid array bounds warnings in vec ops
Building with GCC with -Warray-bounds enabled there are several warnings
in sstep.c along the lines of:
In function ‘do_byte_reverse’,
inlined from ‘do_vec_load’ at arch/powerpc/lib/sstep.c:691:3,
inlined from ‘emulate_loadstore’ at arch/powerpc/lib/sstep.c:3439:9:
arch/powerpc/lib/sstep.c:289:23: error: array subscript 2 is outside array bounds of ‘u8[16]’ {aka ‘unsigned char[16]’} [-Werror=array-bounds=]
289 | up[2] = byterev_8(up[1]);
| ~~~~~~^~~~~~~~~~~~~~~~~~
arch/powerpc/lib/sstep.c: In function ‘emulate_loadstore’:
arch/powerpc/lib/sstep.c:681:11: note: at offset 16 into object ‘u’ of size 16
681 | } u = {};
| ^
do_byte_reverse() supports a size up to 32 bytes, but in these cases the
caller is only passing a 16 byte buffer. In practice there is no bug,
do_vec_load() is only called from the LOAD_VMX case in emulate_loadstore().
That in turn is only reached when analyse_instr() recognises VMX ops,
and in all cases the size is no greater than 16:
$ git grep -w LOAD_VMX arch/powerpc/lib/sstep.c
arch/powerpc/lib/sstep.c: op->type = MKOP(LOAD_VMX, 0, 1);
arch/powerpc/lib/sstep.c: op->type = MKOP(LOAD_VMX, 0, 2);
arch/powerpc/lib/sstep.c: op->type = MKOP(LOAD_VMX, 0, 4);
arch/powerpc/lib/sstep.c: op->type = MKOP(LOAD_VMX, 0, 16);
Similarly for do_vec_store().
Although the warning is incorrect, the code would be safer if it clamped
the size from the caller to the known size of the buffer. Do that using
min_t().
Reported-by: Bagas Sanjaya <bagasdotme@gmail.com>
Closes: https://lore.kernel.org/linuxppc-dev/YpbUcPrm61RLIiZF@debian.me/
Reported-by: Jan-Benedict Glaw <jbglaw@lug-owl.de>
Closes: https://lore.kernel.org/linuxppc-dev/20221212215117.aa7255t7qd6yefk4@lug-owl.de/
Reported-by: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Closes: https://lore.kernel.org/linuxppc-dev/6a8bf78c-aedb-4d5a-b0aa-82a51a17b884@embeddedor.com/
Reviewed-by: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Build-tested-by: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20231120235436.1569255-1-mpe@ellerman.id.au
Diffstat (limited to 'arch/powerpc/lib')
| -rw-r--r-- | arch/powerpc/lib/sstep.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c index a4ab8625061a..a13f05cfc7db 100644 --- a/arch/powerpc/lib/sstep.c +++ b/arch/powerpc/lib/sstep.c @@ -688,7 +688,7 @@ static nokprobe_inline int do_vec_load(int rn, unsigned long ea, if (err) return err; if (unlikely(cross_endian)) - do_byte_reverse(&u.b[ea & 0xf], size); + do_byte_reverse(&u.b[ea & 0xf], min_t(size_t, size, sizeof(u))); preempt_disable(); if (regs->msr & MSR_VEC) put_vr(rn, &u.v); @@ -719,7 +719,7 @@ static nokprobe_inline int do_vec_store(int rn, unsigned long ea, u.v = current->thread.vr_state.vr[rn]; preempt_enable(); if (unlikely(cross_endian)) - do_byte_reverse(&u.b[ea & 0xf], size); + do_byte_reverse(&u.b[ea & 0xf], min_t(size_t, size, sizeof(u))); return copy_mem_out(&u.b[ea & 0xf], ea, size, regs); } #endif /* CONFIG_ALTIVEC */ |