diff options
| author | Matt Evans <mev@rivosinc.com> | 2023-02-01 21:39:48 +0300 |
|---|---|---|
| committer | Arnd Bergmann <arnd@arndb.de> | 2023-02-03 17:31:23 +0300 |
| commit | 6246541522845a443b7ae4a8f0e16facc5a91198 (patch) | |
| tree | 7dccf933fb3a592cf1abc68b044f637041e83d67 /include/asm-generic | |
| parent | 88603b6dc419445847923fcb7fe5080067a30f98 (diff) | |
| download | linux-6246541522845a443b7ae4a8f0e16facc5a91198.tar.xz | |
locking/atomic: cmpxchg: Make __generic_cmpxchg_local compare against zero-extended 'old' value
__generic_cmpxchg_local takes unsigned long old/new arguments which
might end up being up-cast from smaller signed types (which will
sign-extend). The loaded compare value must be compared against a
truncated smaller type, so down-cast appropriately for each size.
The issue is apparent on 64-bit machines with code, such as
atomic_dec_unless_positive(), that sign-extends from int.
64-bit machines generally don't use the generic cmpxchg but
development/early ports might make use of it, so make it correct.
Signed-off-by: Matt Evans <mev@rivosinc.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Diffstat (limited to 'include/asm-generic')
| -rw-r--r-- | include/asm-generic/cmpxchg-local.h | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/include/asm-generic/cmpxchg-local.h b/include/asm-generic/cmpxchg-local.h index 380cdc824e4b..c3e7315b7c1d 100644 --- a/include/asm-generic/cmpxchg-local.h +++ b/include/asm-generic/cmpxchg-local.h @@ -26,15 +26,15 @@ static inline unsigned long __generic_cmpxchg_local(volatile void *ptr, raw_local_irq_save(flags); switch (size) { case 1: prev = *(u8 *)ptr; - if (prev == old) + if (prev == (u8)old) *(u8 *)ptr = (u8)new; break; case 2: prev = *(u16 *)ptr; - if (prev == old) + if (prev == (u16)old) *(u16 *)ptr = (u16)new; break; case 4: prev = *(u32 *)ptr; - if (prev == old) + if (prev == (u32)old) *(u32 *)ptr = (u32)new; break; case 8: prev = *(u64 *)ptr; |