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authorRich Felker <dalias@aerifal.cx>2022-01-09 00:33:56 -0500
committerRich Felker <dalias@aerifal.cx>2022-01-09 00:33:56 -0500
commit52f0deb96975401d9f13334dc37f907630224af7 (patch)
treeaf9613d907f834ef4af453846ace727cd1ae7cb1 /src
parentcbacd638e32a02edbe66c48ae3d1361bc06a492a (diff)
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make fseek detect and produce an error for invalid whence arguments
this is a POSIX requirement. we previously relied on the underlying fd (or other backend) seek operation to produce the error, but since linux lseek now supports other seek modes (SEEK_DATA and SEEK_HOLE) which do not interact well with stdio buffering, this is insufficient. instead, explicitly check whence before performing any operations.
Diffstat (limited to 'src')
-rw-r--r--src/stdio/fseek.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/src/stdio/fseek.c b/src/stdio/fseek.c
index 439308f7..c07f7e95 100644
--- a/src/stdio/fseek.c
+++ b/src/stdio/fseek.c
@@ -1,7 +1,14 @@
#include "stdio_impl.h"
+#include <errno.h>
int __fseeko_unlocked(FILE *f, off_t off, int whence)
{
+ /* Fail immediately for invalid whence argument. */
+ if (whence != SEEK_CUR && whence != SEEK_SET && whence != SEEK_END) {
+ errno = EINVAL;
+ return -1;
+ }
+
/* Adjust relative offset for unread data in buffer, if any. */
if (whence == SEEK_CUR && f->rend) off -= f->rend - f->rpos;