5.10-stable review patch. If anyone has any objections, please let me know.
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From: Kees Cook kees@kernel.org
[ Upstream commit d19d638b1e6cf746263ef60b7d0dee0204d8216a ]
Modern (fortified) memcpy() prefers to avoid writing (or reading) beyond the end of the addressed destination (or source) struct member:
In function ‘fortify_memcpy_chk’, inlined from ‘syscall_get_arguments’ at ./arch/x86/include/asm/syscall.h:85:2, inlined from ‘populate_seccomp_data’ at kernel/seccomp.c:258:2, inlined from ‘__seccomp_filter’ at kernel/seccomp.c:1231:3: ./include/linux/fortify-string.h:580:25: error: call to ‘__read_overflow2_field’ declared with attribute warning: detected read beyond size of field (2nd parameter); maybe use struct_group()? [-Werror=attribute-warning] 580 | __read_overflow2_field(q_size_field, size); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
As already done for x86_64 and compat mode, do not use memcpy() to extract syscall arguments from struct pt_regs but rather just perform direct assignments. Binary output differences are negligible, and actually ends up using less stack space:
- sub $0x84,%esp + sub $0x6c,%esp
and less text size:
text data bss dec hex filename 10794 252 0 11046 2b26 gcc-32b/kernel/seccomp.o.stock 10714 252 0 10966 2ad6 gcc-32b/kernel/seccomp.o.after
Closes: https://lore.kernel.org/lkml/9b69fb14-df89-4677-9c82-056ea9e706f5@gmail.com/ Reported-by: Mirsad Todorovac mtodorovac69@gmail.com Signed-off-by: Kees Cook kees@kernel.org Signed-off-by: Dave Hansen dave.hansen@linux.intel.com Reviewed-by: Gustavo A. R. Silva gustavoars@kernel.org Acked-by: Dave Hansen dave.hansen@linux.intel.com Tested-by: Mirsad Todorovac mtodorovac69@gmail.com Link: https://lore.kernel.org/all/20240708202202.work.477-kees%40kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/include/asm/syscall.h | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/syscall.h b/arch/x86/include/asm/syscall.h index 7cbf733d11afd..e8a28380d0ade 100644 --- a/arch/x86/include/asm/syscall.h +++ b/arch/x86/include/asm/syscall.h @@ -85,7 +85,12 @@ static inline void syscall_get_arguments(struct task_struct *task, struct pt_regs *regs, unsigned long *args) { - memcpy(args, ®s->bx, 6 * sizeof(args[0])); + args[0] = regs->bx; + args[1] = regs->cx; + args[2] = regs->dx; + args[3] = regs->si; + args[4] = regs->di; + args[5] = regs->bp; }
static inline void syscall_set_arguments(struct task_struct *task,