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The underlying cause lies in a data structure mismatch between the variable allocation space in user-space and the ioctl encoding expectations defined by Linux: the ioctl command token incorporates the 'long' primitive data size, so the kernel explicitly encodes a 64-bit target memory region pointer when deployed on x86_64. FUSE driver enforce the _IOR-decoded payload envelope, hence it uses 8-byte buffer to accommodate the incoming user-space daemon response. When finalizing the ioctl transaction back down to user space, it writes all 8-bytes directly into the 4-bytes memory reference provided by e2fsprogs. Reproduce: compile with '-fstack-protector-strong' and '-D_FORTIFY_SOURCE=3' (fedor44, 7.2.5-200.fc44.x86_64): $ lsattr -v ./foo *** stack smashing detected ***: terminated Aborted (core dumped) lsattr -v ./foo Solution: change ioctl arg to 'long' but use only lower 32-bits of result. Signed-off-by: Shachar Sharon --- lib/e2p/fgetversion.c | 4 ++-- lib/e2p/fsetversion.c | 7 ++++--- 2 files changed, 6 insertions(+), 5 deletions(-) diff --git a/lib/e2p/fgetversion.c b/lib/e2p/fgetversion.c index f3a5b4cd..eaac46c6 100644 --- a/lib/e2p/fgetversion.c +++ b/lib/e2p/fgetversion.c @@ -45,7 +45,7 @@ int fgetversion(const char *name, unsigned long *version) { - unsigned int ver = -1; + long ver = 0; int rc = -1; #if HAVE_EXT2_IOCTLS # if !APPLE_DARWIN @@ -68,7 +68,7 @@ int fgetversion(const char *name, unsigned long *version) errno = EOPNOTSUPP; #endif /* ! HAVE_EXT2_IOCTLS */ if (rc == 0) - *version = ver; + *version = (unsigned long)ver & 0xffffffffUL; return rc; } diff --git a/lib/e2p/fsetversion.c b/lib/e2p/fsetversion.c index 5f844b55..9b599c19 100644 --- a/lib/e2p/fsetversion.c +++ b/lib/e2p/fsetversion.c @@ -47,12 +47,13 @@ int fsetversion (const char * name, unsigned long version) { #if HAVE_EXT2_IOCTLS #if !APPLE_DARWIN - int fd, r, ver, save_errno = 0; + int fd, r, save_errno = 0; + long ver; fd = open (name, OPEN_FLAGS); if (fd == -1) return -1; - ver = (int) version; + ver = (long) (version & 0xffffffffUL); r = ioctl (fd, EXT2_IOC_SETVERSION, &ver); if (r == -1) save_errno = errno; @@ -61,7 +62,7 @@ int fsetversion (const char * name, unsigned long version) errno = save_errno; return r; #else - int ver = (int)version; + long ver = (long)(version & 0xffffffffUL); return syscall(SYS_fsctl, name, EXT2_IOC_SETVERSION, &ver, 0); #endif #else /* ! HAVE_EXT2_IOCTLS */ -- 2.55.0