5.4-stable review patch. If anyone has any objections, please let me know.
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From: Arnd Bergmann arnd@arndb.de
commit 4b8e88e563b5f666446d002ad0dc1e6e8e7102b0 upstream.
The old ftruncate() syscall, using the 32-bit off_t misses a sign extension when called in compat mode on 64-bit architectures. As a result, passing a negative length accidentally succeeds in truncating to file size between 2GiB and 4GiB.
Changing the type of the compat syscall to the signed compat_off_t changes the behavior so it instead returns -EINVAL.
The native entry point, the truncate() syscall and the corresponding loff_t based variants are all correct already and do not suffer from this mistake.
Fixes: 3f6d078d4acc ("fix compat truncate/ftruncate") Reviewed-by: Christian Brauner brauner@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Arnd Bergmann arnd@arndb.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/open.c | 4 ++-- include/linux/compat.h | 2 +- include/linux/syscalls.h | 2 +- 3 files changed, 4 insertions(+), 4 deletions(-)
--- a/fs/open.c +++ b/fs/open.c @@ -200,13 +200,13 @@ out: return error; }
-SYSCALL_DEFINE2(ftruncate, unsigned int, fd, unsigned long, length) +SYSCALL_DEFINE2(ftruncate, unsigned int, fd, off_t, length) { return do_sys_ftruncate(fd, length, 1); }
#ifdef CONFIG_COMPAT -COMPAT_SYSCALL_DEFINE2(ftruncate, unsigned int, fd, compat_ulong_t, length) +COMPAT_SYSCALL_DEFINE2(ftruncate, unsigned int, fd, compat_off_t, length) { return do_sys_ftruncate(fd, length, 1); } --- a/include/linux/compat.h +++ b/include/linux/compat.h @@ -567,7 +567,7 @@ asmlinkage long compat_sys_fstatfs(unsig asmlinkage long compat_sys_fstatfs64(unsigned int fd, compat_size_t sz, struct compat_statfs64 __user *buf); asmlinkage long compat_sys_truncate(const char __user *, compat_off_t); -asmlinkage long compat_sys_ftruncate(unsigned int, compat_ulong_t); +asmlinkage long compat_sys_ftruncate(unsigned int, compat_off_t); /* No generic prototype for truncate64, ftruncate64, fallocate */ asmlinkage long compat_sys_openat(int dfd, const char __user *filename, int flags, umode_t mode); --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -422,7 +422,7 @@ asmlinkage long sys_fstatfs(unsigned int asmlinkage long sys_fstatfs64(unsigned int fd, size_t sz, struct statfs64 __user *buf); asmlinkage long sys_truncate(const char __user *path, long length); -asmlinkage long sys_ftruncate(unsigned int fd, unsigned long length); +asmlinkage long sys_ftruncate(unsigned int fd, off_t length); #if BITS_PER_LONG == 32 asmlinkage long sys_truncate64(const char __user *path, loff_t length); asmlinkage long sys_ftruncate64(unsigned int fd, loff_t length);