From 35b9eb0a72b6254568a294f0ebd011da20958a64 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= Date: Fri, 6 Dec 2019 12:13:34 +0100 Subject: [PATCH] basic/efivars: do not return EIO if an efivar read is shorten than fstat size On my machine stat returns size 22, but only 20 bytes are read: openat(AT_FDCWD, "/sys/firmware/efi/efivars/LoaderTimeInitUSec-4a67b082-0a4c-41cf-b6c7-440b29bb8c4f", O_RDONLY|O_NOCTTY|O_CLOEXEC) = 3 fstat(3, {st_mode=S_IFREG|0644, st_size=22, ...}) = 0 read(3, "\6\0\0\0", 4) = 4 read(3, "7\0001\0001\0003\0005\0002\0007\0\0\0", 18) = 16 Failed to read LoaderTimeInitUSec: Input/output error Let's just accept that the kernel is returning inconsistent results. It seems to happen two only two variables on my machine: /sys/firmware/efi/efivars/LoaderTimeInitUSec-4a67b082-0a4c-41cf-b6c7-440b29bb8c4f /sys/firmware/efi/efivars/LoaderTimeMenuUSec-4a67b082-0a4c-41cf-b6c7-440b29bb8c4f so it might be related to the way we write them. --- src/basic/efivars.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/src/basic/efivars.c b/src/basic/efivars.c index 7b14c062df1..bfde67a883b 100644 --- a/src/basic/efivars.c +++ b/src/basic/efivars.c @@ -90,13 +90,14 @@ int efi_get_variable( n = read(fd, buf, (size_t) st.st_size - 4); if (n < 0) return -errno; - if (n != st.st_size - 4) - return -EIO; + assert(n <= st.st_size - 4); /* Always NUL terminate (2 bytes, to protect UTF-16) */ - ((char*) buf)[st.st_size - 4] = 0; - ((char*) buf)[st.st_size - 4 + 1] = 0; - } + ((char*) buf)[n - 4] = 0; + ((char*) buf)[n - 4 + 1] = 0; + } else + /* Assume that the reported size is accurate */ + n = st.st_size - 4; /* Note that efivarfs interestingly doesn't require ftruncate() to update an existing EFI variable * with a smaller value. */ @@ -108,7 +109,7 @@ int efi_get_variable( *ret_value = TAKE_PTR(buf); if (ret_size) - *ret_size = (size_t) st.st_size - 4; + *ret_size = n; return 0; }